rtlwifi: rtl8192ce: rtl8192cu: Fix multiple def errors for allyesconfig build

As noted by Stephan Rothwell, an allyesconfig build fails since rtl8192cu
was merged with failures such as:

drivers/net/wireless/rtlwifi/rtl8192cu/built-in.o: In function `rtl92c_phy_sw_chnl':
(.opd+0xf30): multiple definition of `rtl92c_phy_sw_chnl'
drivers/net/wireless/rtlwifi/rtl8192ce/built-in.o:(.opd+0xb70): first defined here
drivers/net/wireless/rtlwifi/rtl8192cu/built-in.o: In function `rtl92c_fill_h2c_cmd':
(.opd+0x288): multiple definition of `rtl92c_fill_h2c_cmd'
drivers/net/wireless/rtlwifi/rtl8192ce/built-in.o:(.opd+0x288): first defined here

These are caused because the code shared between rtl8192ce and rtl8192cu
is included in both drivers. This has been fixed by creating a new modue that
contains the shared code.

Signed-off-by: Larry Finger <Larry.Finger@lwfinger.net>
Signed-off-by: John W. Linville <linville@tuxdriver.com>