rtl8xxxu: move rtl8188[cr] and rtl8192c related code into rtl8xxxu_8192c.c

This moves the code for rtl8188c, rtl8188r, and rtl8192c into it's own
file. This is purely a code moving exercise, there is no change to the
code itself.

Signed-off-by: Jes Sorensen <Jes.Sorensen@redhat.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>