ARM: dts: Disable the RTC by default on exynos5

This change makes the rtc on the exynos5250 and 5440 disabled by
default to match exynos4.

Ever since the common clock framework came in, exynos5250 boards
have dumped lots of warnings in the boot log. It turns out that
we don't see those on exynos4 since the rtc is disabled by default.
While we need to get to the bottom of the problems with the RTC,
it still makes sense to have the default state of the RTC on exynos
boards match.

For the record, warnings look like this:
  ------------[ cut here ]------------
  WARNING: at drivers/clk/clk.c:771 __clk_enable+0x34/0xb0()
  Modules linked in:
  [<80015bfc>] (unwind_backtrace+0x0/0xec) from [<804717f0>] (dump_stack+0x20/0x24)
  [<804717f0>] (dump_stack+0x20/0x24) from [<80023cd0>] (warn_slowpath_common+0x5c/0x7c)
  [<80023cd0>] (warn_slowpath_common+0x5c/0x7c) from [<80023d1c>] (warn_slowpath_null+0x2c/0x34)
  [<80023d1c>] (warn_slowpath_null+0x2c/0x34) from [<8035ddb0>] (__clk_enable+0x34/0xb0)
  [<8035ddb0>] (__clk_enable+0x34/0xb0) from [<8035de54>] (clk_enable+0x28/0x3c)
  [<8035de54>] (clk_enable+0x28/0x3c) from [<8031a160>] (s3c_rtc_probe+0xf4/0x434)
  [<8031a160>] (s3c_rtc_probe+0xf4/0x434) from [<8028e288>] (platform_drv_probe+0x24/0x28)
  [<8028e288>] (platform_drv_probe+0x24/0x28) from [<8028ce10>] (driver_probe_device+0xbc/0x22c)
  [<8028ce10>] (driver_probe_device+0xbc/0x22c) from [<8028cff8>] (__driver_attach+0x78/0x9c)
  [<8028cff8>] (__driver_attach+0x78/0x9c) from [<8028bdfc>] (bus_for_each_dev+0x64/0xac)
  [<8028bdfc>] (bus_for_each_dev+0x64/0xac) from [<8028c7e0>] (driver_attach+0x28/0x30)
  [<8028c7e0>] (driver_attach+0x28/0x30) from [<8028c43c>] (bus_add_driver+0xe0/0x234)
  [<8028c43c>] (bus_add_driver+0xe0/0x234) from [<8028d55c>] (driver_register+0xac/0x13c)
  [<8028d55c>] (driver_register+0xac/0x13c) from [<8028e4f4>] (platform_driver_register+0x54/0x68)
  [<8028e4f4>] (platform_driver_register+0x54/0x68) from [<8065c944>] (s3c_rtc_driver_init+0x14/0x1c)
  [<8065c944>] (s3c_rtc_driver_init+0x14/0x1c) from [<800086d8>] (do_one_initcall+0x60/0x138)
  [<800086d8>] (do_one_initcall+0x60/0x138) from [<80633a8c>] (kernel_init_freeable+0x108/0x1d0)
  [<80633a8c>] (kernel_init_freeable+0x108/0x1d0) from [<8046d2f8>] (kernel_init+0x1c/0xf4)
  [<8046d2f8>] (kernel_init+0x1c/0xf4) from [<8000e358>] (ret_from_fork+0x14/0x20)
  ---[ end trace 4bcdc801c868d73f ]---

Signed-off-by: Doug Anderson <dianders@chromium.org>
Signed-off-by: Kukjin Kim <kgene.kim@samsung.com>
Signed-off-by: Olof Johansson <olof@lixom.net>