rtlwifi: Convert to asynchronous firmware load

This patch addresses a kernel bugzilla report and two recent mail threads.

The kernel bugzilla report is https://bugzilla.kernel.org/show_bug.cgi?id=42632,
which reports a udev timeout on boot.

The first mail thread, which was on LKML (http://lkml.indiana.edu/hypermail/
linux/kernel/1112.3/00965.html) was for a WARNING that occurs after a
suspend/resume cycle for rtl8192cu.

The scond mail thread (http://marc.info/?l=linux-wireless&m=132655490826766&w=2

)
concerned changes in udev that break drivers that delay while firmware is loaded
on modprobe.

This patch converts all rtlwifi-based drivers to use the asynchronous firmware
loading mechanism. Drivers rtl8192ce, rtl8192cu and rtl8192de share a common
callback routine. Driver rtl8192se needs different handling of the firmware,
thus it has its own code.

Signed-off-by: Larry Finger <Larry.Finger@lwfinger.net>
Cc: Stable <stable@vger.kernel.org>
Signed-off-by: John W. Linville <linville@tuxdriver.com>