clk: qcom: 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: I95ddc99b84a44859bb680e5c3da30eec74394016
Signed-off-by: Taniya Das <tdas@codeaurora.org>