drivers: qcom: rpmh_master_stat: remove stub function definition

In order to support early merge of code, a vestigial definition for
qcom_smem_get() was added. This was accidentally merged in. Let's remove
it and allow the RPMH master stats to be read from the memory.

Change-Id: I89dc45c6edd8fb0df01416f7d9fb95feb1dfacc2
Signed-off-by: Lina Iyer <ilina@codeaurora.org>