drivers: regulator: Drop rpm_smd_regulator_driver_init export

WARNING: vmlinux.o(___ksymtab+rpm_smd_regulator_driver_init+0x0):
  Section mismatch in reference from the variable
  __ksymtab_rpm_smd_regulator_driver_init to the function
  .init.text:rpm_smd_regulator_driver_init()
The symbol rpm_smd_regulator_driver_init is exported and annotated
  __init
Fix this by removing the __init annotation of
  rpm_smd_regulator_driver_init or drop the export.

FATAL: modpost: Section mismatches detected.
Change-Id: I2d199cec156f573f7ea6b8ca01d34a48b449cd61