boot/bootutil/loader: fix comparison using fih_eq() in hook service

This commit fixes following issue:
One of parameters in comparison using fih_eq() was not of fih_int
type which caused build error when medium or higher FIH mode is enabled.

Signed-off-by: Andrzej Puzdrowski <andrzej.puzdrowski@nordicsemi.no>
diff --git a/boot/bootutil/src/loader.c b/boot/bootutil/src/loader.c
index 8816d63..b47edf2 100644
--- a/boot/bootutil/src/loader.c
+++ b/boot/bootutil/src/loader.c
@@ -767,7 +767,7 @@
 #endif
     BOOT_HOOK_CALL_FIH(boot_image_check_hook, fih_int_encode(BOOT_HOOK_REGULAR),
                        fih_rc, BOOT_CURR_IMG(state), slot);
-    if (fih_eq(fih_rc, BOOT_HOOK_REGULAR))
+    if (fih_eq(fih_rc, fih_int_encode(BOOT_HOOK_REGULAR)))
     {
         FIH_CALL(boot_image_check, fih_rc, state, hdr, fap, bs);
     }