clk: msm: osm: Update maximum number of bytes to read from buffer

Currently the number of maximum bytes to be copied from buffer is
incorrectly using the size of buffer. Replace to use the count
which is the maximum number of bytes to be read.

Change-Id: I797c4dc0af626e347dfef43a754d0c469585ba55
Signed-off-by: Taniya Das <tdas@codeaurora.org>