msm: ipa4: Fix to overcome KW issues

Correct the validation of number of dma entries in DMA table
to overcome the out-of-bounds access to dma buffers array.
And make changes to initialize an uninitialized variable
which may contain junk data.

Change-Id: Ia05082c887548e58831ab7dfae42cba97ec13fec
Signed-off-by: Praveen Kurapati <pkurapat@codeaurora.org>