Pass correct string argument to perror

Fix this compiler warning

hmx_upgrade_flash.c:176:5: warning: passing argument 1 of 'perror' from
incompatible pointer type

Change-Id: I95badfd4dca434fc3aed1cacbd9b1609fe9de660
diff --git a/libupgrade/hmx_upgrade_flash.c b/libupgrade/hmx_upgrade_flash.c
index 9f9ae2c..7db26be 100644
--- a/libupgrade/hmx_upgrade_flash.c
+++ b/libupgrade/hmx_upgrade_flash.c
@@ -177,7 +177,7 @@
 
   ret = lseek(fd_nvram, offset, SEEK_SET);
   if(ret < 0) {
-    perror(lseek);
+    perror("lseek");
     return -1;
   }