regulator: fix build when CONFIG_REGULATOR_DUMMY=n

regulator: fix build when CONFIG_REGULATOR_DUMMY=n

Commit f03f91826 (regulator: Add option for machine drivers
to enable the dummy regulator) in the regulators tree
seems to have introduced the following build break when
CONFIG_REGULATOR_DUMMY is disabled. Fix this.

  CC      drivers/regulator/dummy.o
drivers/regulator/dummy.c:41: error: redefinition of 'regulator_dummy_init'
drivers/regulator/dummy.h:28: note: previous definition of 'regulator_dummy_init' was here
make[2]: *** [drivers/regulator/dummy.o] Error 1
make[1]: *** [drivers/regulator] Error 2
make: *** [drivers] Error 2

Signed-off-by: Anand Gadiyar <gadiyar@ti.com>
Cc: Liam Girdwood <lrg@slimlogic.co.uk>
Cc: Mark Brown <broonie@opensource.wolfsonmicro.com>
Acked-by: Randy Dunlap <randy.dunlap@oracle.com>
Acked-by: Mark Brown <broonie@opensource.wolfsonmicro.com>
Signed-off-by: Liam Girdwood <lrg@slimlogic.co.uk>