kernel: increase bootfs.paq compression level and blocksize

With the intel wifi firmware, this saves around 3MB of the
kernel image size.

sys/src/9/boot/bootmkfile

@@ -18,5 +18,5 @@ bootfs.paq:	$BOOTFSPROTO `{disk/mkfs -aos / $BOOTFSPROTO >[2]/dev/null}
 		cd bootfs/$objtype/bin
 		#strip * */* */*/* >[2]/dev/null || status=''
 	}
-	mkpaqfs -o $target bootfs
+	mkpaqfs -9 -b 65536 -o $target bootfs
 	rm -rf bootfs