mfd: Rename twl4030_ routines in rtc-twl.c

This patch renames all twl4030_ functions to twl_ so that RTC driver can be
shared between Triton and Phoenix.

Signed-off-by: Balaji T K <balajitk@ti.com>
Signed-off-by: Nayak Rajendra <rnayak@ti.com>
Signed-off-by: Santosh Shilimkar <santosh.shilimkar@ti.com>
Acked-by: Kevin Hilman <khilman@deeprootsystems.com>
Signed-off-by: Samuel Ortiz <sameo@linux.intel.com>