soc: qcom: ocmem: make the core clock optional

soc: qcom: ocmem: make the core clock optional

OCMEM's core clock (aka RPM bus 2 clock) is being handled internally by
the interconnect driver. Corresponding clock has been dropped from the
SMD RPM clock driver. The users of the ocmem will vote on the ocmemnoc
interconnect paths, making sure that ocmem is on. Make the clock
optional, keeping it for compatibility with older DT.

Fixes: d6edc31f3a68 ("clk: qcom: smd-rpm: Separate out interconnect bus clocks")
Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@oss.qualcomm.com>
Reviewed-by: Konrad Dybcio <konrad.dybcio@oss.qualcomm.com>
Link: https://lore.kernel.org/r/20260323-ocmem-v1-1-ad9bcae44763@oss.qualcomm.com
Signed-off-by: Bjorn Andersson <andersson@kernel.org>