ASoC: msm: fix integer overflow for long duration offload playback

32 bit variable is used for storing number of bytes copied to DSP,
which can overflow when playback duration goes beyond 24 hours.
Change data type for this variable to uint64_t, to prevent overflow
and related playback anomaly.

CRs-Fixed: 877677
Change-Id: Ie4dfa630cf89559bb784d4712c52526665baeca6
Signed-off-by: Dhananjay Kumar <dhakumar@codeaurora.org>