msm: kgsl: Directly return page size of the supported pool

In current code, if a request comes to allocate a page of a size
for which pool is not supported EAGAIN is returned with a page
size of PAGE_SIZE << --order. This is not efficient as it results
in multiple retries in case pool of size = PAGE_SIZE << --order is
also not supported.

Instead of retrying with lower order page in a sequential manner
this change directly returns the page size of the pool that is
supported.

Change-Id: Ib82ae5be7e4109fdc0a3d72bcbcd4b47cfb2e266
Signed-off-by: Deepak Kumar <dkumar@codeaurora.org>