FROMGIT: clk: qcom: clk-rcg2: Introduce a cfg offset for RCGs

The RCG CFG/M/N/D register base could be at a different offset than
the CMD register, so introduce a cfg_offset to identify the offset
with respect to the CMD RCGR register.

(cherry picked from commit 96dc791d
https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git

)

Signed-off-by: Taniya Das <tdas@codeaurora.org>
Signed-off-by: Anu Ramanathan <anur@codeaurora.org>
Signed-off-by: Shawn Guo <shawn.guo@linaro.org>
Signed-off-by: Vinod Koul <vkoul@kernel.org>
Signed-off-by: Khasim Syed Mohammed <khasim.mohammed@linaro.org>
Change-Id: Ie4f13ee56505784234fcd75f42b84035b08dabcf