Add fit-dtb.blob* to .gitignore.

Support for compressed fit-dtb.blob was added in:

  commit 95f4bbd5 ("lib: fdt: Allow LZO and GZIP DT compression in
  U-Boot")

Adjust .gitignore to also exclude compressed blobs.
Signed-off-by: NVagrant Cascadian <vagrant@reproducible-builds.org>

.gitignore

@@ -35,7 +35,7 @@
 #
 # Top-level generic files
 #
-fit-dtb.blob
+fit-dtb.blob*
 /MLO*
 /SPL*
 /System.map