Fix test failure caused by bad handling of ramdisk

Commit e3a5bbce broke the FIT image tests by not loading a ramdisk even if
a load address is provided in the FIT. The rationale was that a load address
of 0 should be considered to mean 'do not load'.

Add a new load operation which supports this feature, so that the ramdisk
will be loaded if a non-zero load address is provided.

Signed-off-by: Simon Glass <sjg@chromium.org>

common/image.c

@@ -966,7 +966,8 @@ int boot_get_ramdisk(int argc, char * const argv[], bootm_headers_t *images,
 					&fit_uname_config, arch,
 					IH_TYPE_RAMDISK,
 					BOOTSTAGE_ID_FIT_RD_START,
-					FIT_LOAD_IGNORED, &rd_data, &rd_len);
+					FIT_LOAD_OPTIONAL_NON_ZERO,
+					&rd_data, &rd_len);
 			if (rd_noffset < 0)
 				return 1;