MIPS: Ignore vmlinux.*

Signed-off-by: NYoichi Yuasa <yuasa@linux-mips.org>
Cc: linux-mips <linux-mips@linux-mips.org>
Patchwork: http://patchwork.linux-mips.org/patch/795/Signed-off-by: NRalf Baechle <ralf@linux-mips.org>

arch/mips/boot/.gitignore

 mkboot
 elf2ecoff
+vmlinux.*
 zImage
 zImage.tmp