clk: mediatek: fhctl: Mark local variables static

clk: mediatek: fhctl: Mark local variables static

smatch reports
drivers/clk/mediatek/clk-fhctl.c:17:27: warning: symbol
  'fhctl_offset_v1' was not declared. Should it be static?
drivers/clk/mediatek/clk-fhctl.c:30:27: warning: symbol
  'fhctl_offset_v2' was not declared. Should it be static?

These variables are only used in one file so should be static.

Signed-off-by: Tom Rix <trix@redhat.com>
Link: https://lore.kernel.org/r/20230406010935.1944976-1-trix@redhat.com
Fixes: 8da312d6574c ("clk: mediatek: fhctl: Add support for older fhctl register layout")
Signed-off-by: Stephen Boyd <sboyd@kernel.org>