drivers: clk: qcom: Move the PM QoS request structure to static data

Keeping the PM QoS request structure on the stack
may not be a good idea since a) it requires additional
annotation and b) if we ever move the QoS add and remove
requests out of the set_rate function (and just use
update inside), the structure needs to be globally
accessible anyway.

Change-Id: I875cb1b4f2a6620a7508b3ec56a721aa6958255a
Signed-off-by: Vikram Mulukutla <markivx@codeaurora.org>