staging: r8821ae: Enable build by reverting BROKEN marking

When this driver failed to build in the linux-next tree, Stephen Rothwell
modified Kconfig to disable it. Now that the problems are fixed, that
change can be reverted.

Reported-by: Stephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: Larry Finger <Larry.Finger@lwfinger.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>