wlcore: Propagate errors from wl1271_raw_read32

Propagate errors from wl1271_raw_read32. Since the read functions had no
way of returning errors in-band, change their prototypes.
Also rename prefixes of wlcore functions which their prototypes had to
be changed.

Signed-off-by: Ido Yariv <ido@wizery.com>
Signed-off-by: Luciano Coelho <coelho@ti.com>

drivers/net/wireless/ti/wl18xx/io.h

@@ -22,7 +22,7 @@
 #ifndef __WL18XX_IO_H__
 #define __WL18XX_IO_H__
 
-void wl18xx_top_reg_write(struct wl1271 *wl, int addr, u16 val);
-u16 wl18xx_top_reg_read(struct wl1271 *wl, int addr);
+int wl18xx_top_reg_write(struct wl1271 *wl, int addr, u16 val);
+int wl18xx_top_reg_read(struct wl1271 *wl, int addr, u16 *out);
 
 #endif /* __WL18XX_IO_H__ */