lib: Refactor bmp_load_logo() implementation

This refactoring ensures bmp_load_logo() takes logo_size as an
argument, returning a valid logo_ptr only if logo_size is non-zero.

This prevents potential errors from mismatched size assumption.

BUG=b:242829490
TEST=google/rex0 builds successfully.

Change-Id: I14bc54670a67980ec93bc366b274832d1f959e50
Signed-off-by: Subrata Banik <subratabanik@google.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/81618
Reviewed-by: Matt DeVillier <matt.devillier@amd.corp-partner.google.com>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Dinesh Gehlot <digehlot@google.com>
Reviewed-by: Julius Werner <jwerner@chromium.org>

src/lib/bmp_logo.c

@@ -16,25 +16,27 @@ const char *bmp_logo_filename(void)
 }
 #endif
 
-void bmp_load_logo(uint32_t *logo_ptr, uint32_t *logo_size)
+void *bmp_load_logo(size_t *logo_size)
 {
 	void *logo_buffer;
 
 	/* CBMEM is locked for S3 resume path. */
 	if (acpi_is_wakeup_s3())
-		return;
+		return NULL;
 
 	logo_entry = cbmem_entry_add(CBMEM_ID_FSP_LOGO, 1 * MiB);
 	if (!logo_entry)
-		return;
+		return NULL;
 
 	logo_buffer = cbmem_entry_start(logo_entry);
 	if (!logo_buffer)
-		return;
+		return NULL;
 
 	*logo_size = cbfs_load(bmp_logo_filename(), logo_buffer, 1 * MiB);
-	if (*logo_size)
-		*logo_ptr = (uintptr_t)logo_buffer;
+	if (*logo_size == 0)
+		return NULL;
+
+	return logo_buffer;
 }
 
 void bmp_release_logo(void)