x86/platform/intel-mid: Enable RTC on Intel Merrifield

Intel Merrifield has legacy RTC in contrast to the rest on Intel MID
platforms.

Set legacy RTC flag explicitly in architecture initialization code and
allocate interrupt for it.

Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/20170113164355.66161-1-andriy.shevchenko@linux.intel.com


Signed-off-by: Ingo Molnar <mingo@kernel.org>