clk: hisilicon: Mark phase_ops static

Sparse rightfully complains:

drivers/clk/hisilicon/clk-hisi-phase.c:88:22: warning: symbol 'clk_phase_ops' was not declared. Should it be static?
drivers/clk/hisilicon/clk-hisi-phase.c:88:22: warning: symbol 'clk_phase_ops' was not declared. Should it be static?

Signed-off-by: Stephen Boyd <sboyd@kernel.org>