clk: drop unused function __clk_get_flags

clk: drop unused function __clk_get_flags

The function __clk_get_flags has not been used since the April 2019
commit 8284219098b0 ("ARM: omap2+: hwmod: drop CLK_IS_BASIC
flag usage").  Other uses were removed in June 2015, eg by
commit 43afd0689f10 ("clk: Convert __clk_get_flags() to
clk_hw_get_flags()"), which shows how clk_hw_get_flags can easily
be used instead.

Signed-off-by: Julia Lawall <Julia.Lawall@inria.fr>
Link: https://lore.kernel.org/r/1596272022-14173-1-git-send-email-Julia.Lawall@inria.fr
Signed-off-by: Stephen Boyd <sboyd@kernel.org>