sb/amd: Remove dead assignment in SPI driver

Value stored to 'cmd' is never read

Change-Id: I794b6e12f5af272705cd996f7ca5099e9b9dbfc7
Found-by: scan-build from clang 6
Signed-off-by: Paul Menzel <pmenzel@molgen.mpg.de>
Reviewed-on: https://review.coreboot.org/29568
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Angel Pons <th3fanbus@gmail.com>
Reviewed-by: Patrick Georgi <pgeorgi@google.com>
diff --git a/src/southbridge/amd/cimx/sb800/spi.c b/src/southbridge/amd/cimx/sb800/spi.c
index ec18454..574c062 100644
--- a/src/southbridge/amd/cimx/sb800/spi.c
+++ b/src/southbridge/amd/cimx/sb800/spi.c
@@ -95,7 +95,7 @@
 	reset_internal_fifo_pointer();
 	/* Skip the bytes we sent. */
 	for (count = 0; count < bytesout; count++) {
-		cmd = read8((void *)(spibar + 0x0C));
+		read8((void *)(spibar + 0x0C));
 	}
 
 	reset_internal_fifo_pointer();