tegra_pmc_parse_dt() references __initconst data. Fix it to be __init.
This matches its only usage; a call from tegra_pmc_init() which is
already __init. This fixes:

WARNING: vmlinux.o(.text.unlikely+0x580): Section mismatch in reference
from the function tegra_pmc_parse_dt() to the (unknown reference)
.init.rodata:(unknown)
Signed-off-by: Stephen Warren <swarren@nvidia.com>
Signed-off-by: Olof Johansson <olof@lixom.net>