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

"diff -Z" is used to trim the trailing whitespace when comparing the
loaded firmware file with the source firmware file. However, per the
comment in the source code, -Z should not be necessary. In testing, the
input and output files are identical.

Additionally, -Z is not a standard option and is not available in
environments such as busybox. When -Z is not supported, diff fails with
a usage error, which is suppressed, but then causes read_firmwares() to
exit with a false failure message.

Signed-off-by: Dan Rue <dan.rue@linaro.org>
Acked-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Shuah Khan <shuah@kernel.org>

tools/testing/selftests/firmware/fw_filesystem.sh

@@ -155,11 +155,8 @@ read_firmwares()
 {
 	for i in $(seq 0 3); do
 		config_set_read_fw_idx $i
-		# 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" $DIR/read_firmware 2>/dev/null ; then
+		# Verify the contents match
+		if ! diff -q "$FW" $DIR/read_firmware 2>/dev/null ; then
 			echo "request #$i: firmware was not loaded" >&2
 			exit 1
 		fi
@@ -171,7 +168,7 @@ read_firmwares_expect_nofile()
 	for i in $(seq 0 3); do
 		config_set_read_fw_idx $i
 		# Ensures contents differ
-		if diff -q -Z "$FW" $DIR/read_firmware 2>/dev/null ; then
+		if diff -q "$FW" $DIR/read_firmware 2>/dev/null ; then
 			echo "request $i: file was not expected to match" >&2
 			exit 1
 		fi