regulator: lp87565: Enable LP87565_BUCK_CTRL_1_FPWM_MP_0_2

Buck10 is a multi(dual) phase regulator. So as part of enabling it
turn on the LP87565_BUCK_CTRL_1_FPWM_MP_0_2 bit which forces it to
operate always in multiphase and forced-PWM operation mode.
This helps improve the transient voltage response while switching OPP.

Signed-off-by: Keerthy <j-keerthy@ti.com>
Signed-off-by: Mark Brown <broonie@kernel.org>