i.MX28: Reorder battery status functions in SPL

Signed-off-by: Marek Vasut <marek.vasut@gmail.com>
Cc: Detlev Zundel <dzu@denx.de>
Cc: Fabio Estevam <fabio.estevam@freescale.com>
Cc: Stefano Babic <sbabic@denx.de>
Cc: Wolfgang Denk <wd@denx.de>