fs: update fs_dev_part in fs_set_blk_dev_with_part()

As in the case of fs_set_blk_dev(), fs_set_blk_dev_with_part() should
maintain and update fs_dev_part whenever called.

Without this patch, a problem will come up when an efi binary associated
with efi's BOOTxxxx variable is invoked via "bootefi bootmgr".

Signed-off-by: AKASHI Takahiro <takahiro.akashi@linaro.org>
Signed-off-by: Alexander Graf <agraf@suse.de>
diff --git a/fs/fs.c b/fs/fs.c
index adae98d..cb26517 100644
--- a/fs/fs.c
+++ b/fs/fs.c
@@ -365,6 +365,7 @@
 	for (i = 0, info = fstypes; i < ARRAY_SIZE(fstypes); i++, info++) {
 		if (!info->probe(fs_dev_desc, &fs_partition)) {
 			fs_type = info->fstype;
+			fs_dev_part = part;
 			return 0;
 		}
 	}