cpu/x86: compile earlymtrr.c code for romstage as well

In order to make this work earlymtrr.c needed to be removed
from intel/truxton/romstage.c. It's not a ROMCC board so
there's no reason to be including .c files.

Change-Id: If4f5494a53773454b97b90fb856f7e52cadb3f44
Signed-off-by: Andrey Petrov <andrey.petrov@intel.com>
Reviewed-on: https://review.coreboot.org/14094
Tested-by: build bot (Jenkins)
Reviewed-by: Martin Roth <martinroth@google.com>
Reviewed-by: Furquan Shaikh <furquan@google.com>
diff --git a/src/cpu/x86/mtrr/Makefile.inc b/src/cpu/x86/mtrr/Makefile.inc
index cecb826..9b7207b 100644
--- a/src/cpu/x86/mtrr/Makefile.inc
+++ b/src/cpu/x86/mtrr/Makefile.inc
@@ -1 +1,2 @@
 ramstage-y += mtrr.c
+romstage-y += earlymtrr.c