nvmutil: don't reset errno before write

under the current logic, errno would be ECANCELED
if neither checksum is valid, or I/O related if
pwrite fails; alternatively, the for loop exits
and the file has been written, where it is quite
correctly reset already.

ergo, the errno reset at the start of
writeGbeFile is superfluous. remove this bloat.

Signed-off-by: Leah Rowe <leah@libreboot.org>

util/nvmutil/nvmutil.c

@@ -261,7 +261,6 @@ xorswap_buf(int partnum)
 void
 writeGbeFile(void)
 {
-	errno = 0;
 	err_if((cmd == writeGbeFile) && !(validChecksum(0) || validChecksum(1)));
 	for (int p = 0, x = (cmd == writeGbeFile) ? 1 : 0; p < 2; p++) {
 		if ((!nvmPartModified[p]) && (cmd != writeGbeFile))