staging: r8188eu: default to "y" in Kconfig

Two Kconfig entries for this driver default to (uppercase) "Y". But in
Kconfig (lowercase) "y" is a magic symbol. "Y" is an ordinary symbol.
As "Y" is never set these Kconfig symbols will also not be set by
default.

So use "default y" here, as was clearly intended.

Reported-by: Martin Walch <walch.martin@web.de>
Signed-off-by: Paul Bolle <pebolle@tiscali.nl>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>