cbgfx: add load_bitmap

This change adds load_bitmap API, which loads a bitmap file from cbfs
and returns a pointer to the image data.

BUG=none
BRANCH=tot
TEST=Tested on Samus

Change-Id: I7d7874f6f68c414dc877a012ad96c393e42dc35e
Signed-off-by: Patrick Georgi <pgeorgi@google.com>
Original-Commit-Id: 9d33e713a0cf6bd1365418dad989e47e86db01e4
Original-Change-Id: Idbf9682c2fa9df3f0bd296ca47edd02cd09cfd01
Original-Signed-off-by: Daisuke Nojiri <dnojiri@chromium.org>
Original-Reviewed-on: https://chromium-review.googlesource.com/302194
Original-Reviewed-by: Randall Spangler <rspangler@chromium.org>
Reviewed-on: http://review.coreboot.org/11925
Tested-by: build bot (Jenkins)

payloads/libpayload/include/cbgfx.h

@@ -73,6 +73,18 @@ struct rgb_color {
  * y values increasing towards bottom of screen.
  */
 
+/*
+ * Load a bitmap file from cbfs
+ *
+ * Memory is allocated automatically and it's caller's responsibility to free it
+ *
+ * name: name of the bitmap file
+ * size: (OUT) size of the image
+ *
+ * return: pointer to the image data in memory or NULL on error
+ */
+void *load_bitmap(const char *name, size_t *size);
+
 /*
  * draw a box filled with a color on screen
  *