x86/pci: Use MRFLD abbreviation for Merrifield

Everywhere in the kernel the MRFLD is used as abbreviation of Intel Merrifield.
Do the same in intel_mid_pci.c module.

Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Cc: Bjorn Helgaas <bhelgaas@google.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/1468321462-136016-1-git-send-email-andriy.shevchenko@linux.intel.com


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