firmware_loader: revert removal of the fw_fallback_config export

Christoph's patch removed two unsused exported symbols, however, one
symbol is used by the firmware_loader itself.  If CONFIG_FW_LOADER=m so
the firmware_loader is modular but CONFIG_FW_LOADER_USER_HELPER=y we fail
the build at mostpost.

ERROR: modpost: "fw_fallback_config" [drivers/base/firmware_loader/firmware_class.ko] undefined!

This happens because the variable fw_fallback_config is built into the
kernel if CONFIG_FW_LOADER_USER_HELPER=y always, so we need to grant
access to the firmware loader module by exporting it.

Revert only one hunk from his patch.

Fixes: 73960473 ("firmware_loader: remove unused exports")
Reported-by: NRandy Dunlap <rdunlap@infradead.org>
Signed-off-by: NLuis Chamberlain <mcgrof@kernel.org>
Link: https://lore.kernel.org/r/20200424184916.22843-1-mcgrof@kernel.orgSigned-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/base/firmware_loader/fallback_table.c

@@ -21,6 +21,7 @@ struct firmware_fallback_config fw_fallback_config = {
 	.loading_timeout = 60,
 	.old_timeout = 60,
 };
+EXPORT_SYMBOL_GPL(fw_fallback_config);
 
 #ifdef CONFIG_SYSCTL
 struct ctl_table firmware_config_table[] = {