driver: fix a problem with implementation of -falign-foo=0 [PR96247]

driver: fix a problem with implementation of -falign-foo=0 [PR96247]

This patch makes the -falign-foo=0 work as described in the
documentation. Thanks for all the suggestions.

Changelog:
2020-07-27  Hu Jiangping  <hujiangping@cn.fujitsu.com>

	PR driver/96247
	* opts.c (check_alignment_argument): Set the -falign-Name
	on/off flag on and set the -falign-Name string value null,
	when the command-line specified argument is zero.