PM / OPP: Initialize u_volt_min/max to a valid value

We kept u_volt_min/max initialized to 0, when only the target voltage is
present in DT, instead of the target/min/max triplet.

This didn't go well with the regulator framework, as on few calls the
min voltage was set to target and max was set to 0 and so resulted in a
kernel crash like below:

kernel BUG at ../drivers/regulator/core.c:216!

[<c0684af4>] (regulator_check_voltage) from [<c06857ac>] (regulator_set_voltage_unlocked+0x58/0x230)
[<c06857ac>] (regulator_set_voltage_unlocked) from [<c06859ac>] (regulator_set_voltage+0x28/0x54)
[<c06859ac>] (regulator_set_voltage) from [<c0775b28>] (_set_opp_voltage+0x30/0x98)
[<c0775b28>] (_set_opp_voltage) from [<c0776630>] (dev_pm_opp_set_rate+0xf0/0x28c)
[<c0776630>] (dev_pm_opp_set_rate) from [<c096f784>] (__cpufreq_driver_target+0x184/0x2b4)
[<c096f784>] (__cpufreq_driver_target) from [<c0973760>] (dbs_check_cpu+0x1b0/0x1f4)
[<c0973760>] (dbs_check_cpu) from [<c0973f30>] (cpufreq_governor_dbs+0x324/0x5c4)
[<c0973f30>] (cpufreq_governor_dbs) from [<c0970958>] (__cpufreq_governor+0xe4/0x1ec)
[<c0970958>] (__cpufreq_governor) from [<c09711e0>] (cpufreq_init_policy+0x64/0x8c)
[<c09711e0>] (cpufreq_init_policy) from [<c09718cc>] (cpufreq_online+0x2fc/0x708)
[<c09718cc>] (cpufreq_online) from [<c0765ff0>] (subsys_interface_register+0x94/0xd8)
[<c0765ff0>] (subsys_interface_register) from [<c0970530>] (cpufreq_register_driver+0x14c/0x19c)
[<c0970530>] (cpufreq_register_driver) from [<c09746dc>] (dt_cpufreq_probe+0x70/0xec)
[<c09746dc>] (dt_cpufreq_probe) from [<c076907c>] (platform_drv_probe+0x4c/0xb0)
[<c076907c>] (platform_drv_probe) from [<c07678e0>] (driver_probe_device+0x214/0x2c0)
[<c07678e0>] (driver_probe_device) from [<c0767a18>] (__driver_attach+0x8c/0x90)
[<c0767a18>] (__driver_attach) from [<c0765c2c>] (bus_for_each_dev+0x68/0x9c)
[<c0765c2c>] (bus_for_each_dev) from [<c0766d78>] (bus_add_driver+0x1a0/0x218)
[<c0766d78>] (bus_add_driver) from [<c076810c>] (driver_register+0x78/0xf8)
[<c076810c>] (driver_register) from [<c0301d74>] (do_one_initcall+0x90/0x1d8)
[<c0301d74>] (do_one_initcall) from [<c1100e14>] (kernel_init_freeable+0x15c/0x1fc)
[<c1100e14>] (kernel_init_freeable) from [<c0b27a0c>] (kernel_init+0x8/0xf0)
[<c0b27a0c>] (kernel_init) from [<c0307d78>] (ret_from_fork+0x14/0x3c)
Code: e1550004 baffffeb e3a00000 e8bd8070 (e7f001f2)

Fix that by initializing u_volt_min/max to the target voltage in such cases.

Reported-and-tested-by: Krzysztof Kozlowski <k.kozlowski@samsung.com>
Fixes: 27465902 (PM / OPP: Add support to parse "operating-points-v2" bindings)
Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>