image: Drop IMAGE_ENABLE_FIT

Make use of the host Kconfig for FIT. With this we can use
CONFIG_IS_ENABLED(FIT) directly in the host build, so drop the unnecessary
indirection.

Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Alexandru Gagniuc <mr.nuke.me@gmail.com>

arch/arm/mach-imx/hab.c

@@ -591,7 +591,7 @@ static ulong get_image_ivt_offset(ulong img_addr)
 		return (image_get_image_size((image_header_t *)img_addr)
 			+ 0x1000 - 1)  & ~(0x1000 - 1);
 #endif
-#if IMAGE_ENABLE_FIT
+#if CONFIG_IS_ENABLED(FIT)
 	case IMAGE_FORMAT_FIT:
 		return (fit_get_size(buf) + 0x1000 - 1)  & ~(0x1000 - 1);
 #endif