RTL8192CU: Increase max APFM_ONMAC polling count

With certain hardware combinations the poll interval is exceeded before
initialization completes.

Tested on a MacBookPro10,1 using a Sabrent USB-A11N USB adapter.

Signed-off-by: Andy Spencer <andy753421@ucla.edu>
Acked-by: Larry Finger <Larry.Finger@lwfinger.net>
Signed-off-by: John W. Linville <linville@tuxdriver.com>