sh-pfc: sh73a0: Introduce the use of devm_regulator_register

This patch moves data allocated using regulator_register to
devm_regulator_register and does away the calls to regulator_unregister.
The sh73a0_pinmux_soc_exit function is no longer needed and is removed.

Signed-off-by: Himangi Saraogi <himangi774@gmail.com>
Acked-by: Julia Lawall <julia.lawall@lip6.fr>
Acked-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>