ARM: OMAP4: kill omap4_pmic_init and omap4_pmic_get_config

Last user of these functions was deleted in commit
b42b91 ("ARM: OMAP2+: Remove board-omap4panda.c") during DT transition.

Signed-off-by: Nicolae Rosia <Nicolae_Rosia@mentor.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>