baytrail: com1 is a reserved word in windows, rename to uart.c

Coreboot was failing to build on windows because com1
is a reserved keyword under windows.  I'm renaming
it to soc/intel/baytrail/romstage/uart.c.

BUG=None
BRANCH=None
TEST=Built and verified uart.c was compiled in.

Change-Id: I9d1fb65944016e43a08f5c6517d86dc66993b973
Signed-off-by: Martin Roth <martin.roth@se-eng.com>
diff --git a/src/soc/intel/baytrail/romstage/Makefile.inc b/src/soc/intel/baytrail/romstage/Makefile.inc
index 2ec975b..0f41fda 100644
--- a/src/soc/intel/baytrail/romstage/Makefile.inc
+++ b/src/soc/intel/baytrail/romstage/Makefile.inc
@@ -3,4 +3,4 @@
 romstage-y += raminit.c
 romstage-y += gfx.c
 romstage-y += pmc.c
-romstage-$(CONFIG_ENABLE_BUILTIN_COM1) += com1.c
+romstage-$(CONFIG_ENABLE_BUILTIN_COM1) += uart.c
diff --git a/src/soc/intel/baytrail/romstage/com1.c b/src/soc/intel/baytrail/romstage/uart.c
similarity index 100%
rename from src/soc/intel/baytrail/romstage/com1.c
rename to src/soc/intel/baytrail/romstage/uart.c