ds2780_battery&z2_battery: Add __devexit_p at necessary places

According to the comments in include/linux/init.h:

"Pointers to __devexit functions must use __devexit_p(function_name), the
wrapper will insert either the function_name or NULL, depending on the config
options."

Signed-off-by: Axel Lin <axel.lin@gmail.com>
Cc: Clifton Barnes <cabarnes@indesign-llc.com>
Cc: Peter Edwards <sweetlilmre@gmail.com>
Signed-off-by: Anton Vorontsov <cbouatmailru@gmail.com>