bluetooth: fix the concurrency issue while reading from SMD

The function used to read from SMD was causing a deadlock
as it can only be used in interrupt context. As we have
now added tasklet support, we are now reading in tasklet
context, and this patch uses the correct read function
to avoid deadlock.

CRs-Fixed: 314659
Change-Id: I66d1769ada884042169f486ca2aadabde9713b22
Signed-off-by: Ankur Nandwani <ankurn@codeaurora.org>