Revert "selftests: firmware: remove use of non-standard diff -Z option"

This reverts commit f70b472e.

This breaks testing on Debian, and this patch was NACKed anyway.
The proper way to address this is a quirk for busybox as that is
where the issue is present.
Signed-off-by: Luis Chamberlain <mcgrof@kernel.org>
Fixes: f70b472e ("selftests: firmware: remove use of non-standard diff -Z option")
Cc: stable <stable@vger.kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

tools/testing/selftests/firmware/fw_filesystem.sh

@@ -155,8 +155,11 @@ read_firmwares()
 {
 	for i in $(seq 0 3); do
 		config_set_read_fw_idx $i
-		# Verify the contents match
-		if ! diff -q "$FW" $DIR/read_firmware 2>/dev/null ; then
+		# Verify the contents are what we expect.
+		# -Z required for now -- check for yourself, md5sum
+		# on $FW and DIR/read_firmware will yield the same. Even
+		# cmp agrees, so something is off.
+		if ! diff -q -Z "$FW" $DIR/read_firmware 2>/dev/null ; then
 			echo "request #$i: firmware was not loaded" >&2
 			exit 1
 		fi
@@ -168,7 +171,7 @@ read_firmwares_expect_nofile()
 	for i in $(seq 0 3); do
 		config_set_read_fw_idx $i
 		# Ensures contents differ
-		if diff -q "$FW" $DIR/read_firmware 2>/dev/null ; then
+		if diff -q -Z "$FW" $DIR/read_firmware 2>/dev/null ; then
 			echo "request $i: file was not expected to match" >&2
 			exit 1
 		fi