nb/intel/haswell: Fix building BDW MRC.bin path with clang

Clang complains that the two enumerations are incompatible. However, the
values themselves are the same (0: mobile, 1: desktop, 5: ULT). So, cast
the function's return value to silence the warning.

Change-Id: If7b5e22e893e9f3f17a15197c65448fb782590f6
Signed-off-by: Angel Pons <th3fanbus@gmail.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/81862
Reviewed-by: Felix Singer <service+coreboot-gerrit@felixsinger.de>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>

src/northbridge/intel/haswell/broadwell_mrc/raminit.c

@@ -331,7 +331,7 @@ void perform_raminit(const int s3resume)
 
 	struct pei_data pei_data = {
 		.pei_version		= PEI_VERSION,
-		.board_type		= get_pch_platform_type(),
+		.board_type		= (enum board_type)get_pch_platform_type(),
 		.usbdebug		= CONFIG(USBDEBUG),
 		.pciexbar		= CONFIG_ECAM_MMCONF_BASE_ADDRESS,
 		.smbusbar		= CONFIG_FIXED_SMBUS_IO_BASE,