msm: camera: Remove usage of put_ref API in memory manager

Currently if there is a need for kernel to access a buffer,
dma_begin/end is invoked each time. This also occurs in soft irq
ctx leading to a kernel panic due to the usage of mutex in the
begin/end API's. The change removes invoking these API's multiple
times. They will be invoked once during map/unmap respectively.

Change-Id: I598242526ac36d35b1e4638d095313d4d7a2cbf5
Signed-off-by: Karthik Anantha Ram <kartanan@codeaurora.org>