drivers/rtc/rtc-bq4802.c: don't use BIN_2_BCD and BCD_2_BIN

These are going away.

Cc: Takashi Iwai <tiwai@suse.de>
Cc: Adrian Bunk <bunk@stusta.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>