cbfs: Introduce cbfs_ro_map() and cbfs_ro_load()

This patch introduces two new CBFS API functions which are equivalent to
cbfs_map() and cbfs_load(), respectively, with the difference that they
always operate on the read-only CBFS region ("COREBOOT" FMAP section).
Use it to replace some of the simple cases that needed to use
cbfs_locate_file_in_region().

Change-Id: I9c55b022b6502a333a9805ab0e4891dd7b97ef7f
Signed-off-by: Julius Werner <jwerner@chromium.org>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/39306
Reviewed-by: Furquan Shaikh <furquan@google.com>
Reviewed-by: Patrick Georgi <pgeorgi@google.com>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
diff --git a/src/soc/intel/broadwell/raminit.c b/src/soc/intel/broadwell/raminit.c
index e51b4f7..44a8937 100644
--- a/src/soc/intel/broadwell/raminit.c
+++ b/src/soc/intel/broadwell/raminit.c
@@ -80,8 +80,6 @@
 	struct memory_info *mem_info;
 	pei_wrapper_entry_t entry;
 	int ret;
-	struct cbfsf f;
-	uint32_t type = CBFS_TYPE_MRC;
 
 	broadwell_fill_pei_data(pei_data);
 
@@ -114,15 +112,10 @@
 		pei_data->saved_data_size = 0;
 	}
 
-	/* Determine if mrc.bin is in the cbfs. */
-	if (cbfs_locate_file_in_region(&f, "COREBOOT", "mrc.bin", &type) < 0)
-		die("mrc.bin not found!");
 	/* We don't care about leaking the mapping */
-	entry = (pei_wrapper_entry_t)rdev_mmap_full(&f.data);
-	if (entry == NULL) {
-		printk(BIOS_DEBUG, "Couldn't find mrc.bin\n");
-		return;
-	}
+	entry = cbfs_ro_map("mrc.bin", NULL);
+	if (entry == NULL)
+		die("mrc.bin not found!");
 
 	printk(BIOS_DEBUG, "Starting Memory Reference Code\n");