wl1271: Removed wl1271_spi.h and made some functions static

Removed wl1271_spi.h header as there's no more need to access functions
declared there outside of wl1271_spi.c. Also made those SPI access
functions static.

Signed-off-by: Teemu Paasikivi <ext-teemu.3.paasikivi@nokia.com>
Reviewed-by: Juuso Oikarinen <juuso.oikarinen@nokia.com>
Signed-off-by: Juuso Oikarinen <juuso.oikarinen@nokia.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>