util/misc.c: Change offset type for grub_util_write_image_at()

Adding filevercmp support to grub-core/commands/blsuki.c from gnulib will cause
issues with the type of the offset parameter for grub_util_write_image_at() for
emu builds. To fix this issue, we can change the type from off_t to grub_off_t.

Signed-off-by: Alec Brown <alec.r.brown@oracle.com>
Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>

util/misc.c

@@ -101,7 +101,7 @@ grub_util_read_image (const char *path)
 }
 
 void
-grub_util_write_image_at (const void *img, size_t size, off_t offset, FILE *out,
+grub_util_write_image_at (const void *img, size_t size, grub_off_t offset, FILE *out,
 			  const char *name)
 {
   grub_util_info ("writing 0x%" GRUB_HOST_PRIxLONG_LONG " bytes at offset 0x%"