fs: cifs: mute -Wunused-const-variable message

After 'Initial git repository build' commit,
'mapping_table_ERRHRD' variable has not been used.

So 'mapping_table_ERRHRD' const variable could be removed
to mute below warning message:

fs/cifs/netmisc.c:120:40: warning: unused variable 'mapping_table_ERRHRD' [-Wunused-const-variable]
static const struct smb_to_posix_error mapping_table_ERRHRD[] = {
^
Signed-off-by: Austin Kim <[e-mail]>
Signed-off-by: Steve French <[e-mail]>

fs/cifs/netmisc.c

···
 	{0, 0}
 };
 
-static const struct smb_to_posix_error mapping_table_ERRHRD[] = {
-	{0, 0}
-};
-
 /*
  * Convert a string containing text IPv4 or IPv6 address to binary form.
  *