clk: ingenic: Add missing header in cgu.h

The cgu.h has structures that contain 'clk_onecell_data' and 'clk_hw'
structures (no pointers), so the <linux/clk-provider.h> header should be
included.

Signed-off-by: Paul Cercueil <paul@crapouillou.net>
[sboyd@kernel.org: Drop removal of includes in drivers]
Signed-off-by: Stephen Boyd <sboyd@kernel.org>