genpd: move owl-sps-helper.c from drivers/soc

Moving only one of the two files in drivers/soc/actions to drivers/genpd
caused a link failure in allmodconfig, as drivers/genpd is entered
for compile testing, but drivers/soc/actions accidentally got skipped:

x86_64-linux-gnu-ld: vmlinux.o: in function `owl_sps_set_power':
owl-sps.c:(.text+0x16e259d): undefined reference to `owl_sps_set_pg'

Move the other one as well to allow build testing to work correctly.

Reported-by: Stephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>