spi25: Debug flashrom crash when Write Protect is ON

When hardware write protect is applied, flashrom crashed and
generate coredump. spi_disable_blockprotect_generic() calls
flash->chip->printlock() method when disable was failed,
but this method is optional, can be NULL depends on type of
flashrom chip. NULL pointer check before call is added to
avoid crash.

BRANCH=none
BUG=b:129083894
TEST=Run on Mistral P2
(On CR50 console, run "wp disable")
flashrom --wp-range 0 0x400000
flashrom --wp-enable
(On CR50 console, run "wp enable")
flashrom -r /tmp/test.bin
Verify "Block protection could not be disabled!" is shown,
but flash read completes.
Signed-off-by: Yuji Sasaki <sasakiy@chromium.org>

Change-Id: I81094ab5f16a85871fc9869a2e285eddbbbdec4e
Reviewed-on: https://chromium-review.googlesource.com/1535140
Commit-Ready: ChromeOS CL Exonerator Bot <chromiumos-cl-exonerator@appspot.gserviceaccount.com>
Tested-by: Edward O'Callaghan <quasisec@chromium.org>
Reviewed-by: Stefan Reinauer <reinauer@google.com>
Reviewed-by: SANTHOSH JANARDHANA HASSAN <sahassan@google.com>
Reviewed-on: https://review.coreboot.org/c/flashrom/+/40468
Reviewed-by: Stefan Reinauer <stefan.reinauer@coreboot.org>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-on: https://review.coreboot.org/c/flashrom/+/67840
Reviewed-by: Felix Singer <felixsinger@posteo.net>
Reviewed-by: Edward O'Callaghan <quasisec@chromium.org>
Reviewed-by: Nikolai Artemiev <nartemiev@google.com>
Reviewed-by: Angel Pons <th3fanbus@gmail.com>
---
M spi25_statusreg.c
1 file changed, 43 insertions(+), 1 deletion(-)

diff --git a/spi25_statusreg.c b/spi25_statusreg.c
index 05c7acf..de629a9 100644
--- a/spi25_statusreg.c
+++ b/spi25_statusreg.c
@@ -186,7 +186,8 @@
 	status = spi_read_status_register(flash);
 	if ((status & bp_mask) != 0) {
 		msg_cerr("Block protection could not be disabled!\n");
-		flash->chip->printlock(flash);
+		if (flash->chip->printlock)
+			flash->chip->printlock(flash);
 		return 1;
 	}
 	msg_cdbg("disabled.\n");

