powerpc/boot: Update .gitignore

Add a few things that have been missed from .gitignore over the years.
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

arch/powerpc/boot/.gitignore

 addnote
+decompress_inflate.c
 empty.c
 hack-coff
 inffast.c
@@ -13,11 +14,13 @@ infutil.h
 kernel-vmlinux.strip.c
 kernel-vmlinux.strip.gz
 mktree
+otheros.bld
 uImage
 cuImage.*
 dtbImage.*
 *.dtb
 treeImage.*
+vmlinux.strip
 zImage
 zImage.initrd
 zImage.bin.*
@@ -26,6 +29,7 @@ zImage.coff
 zImage.epapr
 zImage.holly
 zImage.*lds
+zImage.maple
 zImage.miboot
 zImage.pmac
 zImage.pseries