clk: qcom: Export gdsc_gx_do_nothing_enable() to modules

A clk driver can be a module but the gdsc code is in the common module.
Export this symbol so that allmodconfig builds keep working.

Cc: Jonathan Marek <jonathan@marek.ca>
Fixes: 0638226d ("clk: qcom: add common gdsc_gx_do_nothing_enable for gpucc drivers")
Signed-off-by: Stephen Boyd <sboyd@kernel.org>
Link: https://lore.kernel.org/r/20200724094025.3261266-1-sboyd@kernel.org