arch/x86/platform/atom: Move pmc_atom to drivers/platform/x86

The pmc_atom driver does not contain any architecture specific
code. It only enables the SoC Power Management Controller driver
for BayTrail and CherryTrail platforms.

Move the pmc_atom driver from arch/x86/platform/atom to
drivers/platform/x86. Also clean-up and reorder include files by
alphabetical order in pmc_atom.h

Signed-off-by: Irina Tirdea <irina.tirdea@intel.com>
Signed-off-by: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
Acked-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Stephen Boyd <sboyd@codeaurora.org>