SPL ext: cosmetic: correct error message in spl_load_image_ext()

Correct the error message in spl_load_image_ext() when image parsing
fails. Instead of "ext4fs_read failed" print "failed to parse image
header".

Signed-off-by: Petr Kulhavy <brain@jikos.cz>
CC: Guillaume GARDET <guillaume.gardet@free.fr>
CC: Tom Rini <trini@konsulko.com>
diff --git a/common/spl/spl_ext.c b/common/spl/spl_ext.c
index 89ac4f4..a85dc85 100644
--- a/common/spl/spl_ext.c
+++ b/common/spl/spl_ext.c
@@ -50,7 +50,7 @@
 
 	err = spl_parse_image_header(header);
 	if (err < 0) {
-		puts("spl: ext4fs_read failed\n");
+		puts("spl: ext: failed to parse image header\n");
 		goto end;
 	}