ALSA: core: Fix crash by avoiding appl_ptr crossing 32-bit boundary 

ncase of A2DP usecase using proxy driver, appl_ptr has
boundary value as 0x60000000 frames in sw_params for stereo(2 channels).
When this value crosses 0x40000000, then userspace calculating
appl_ptr at bytes results in crossing 32-bit value 0x100000000,
and points to 0x0 offset which can result in crash or pop.
To avoid above scenario, set the sw_params appl_ptr boundary value
within 0x40000000. Added proper check at sw_params update
to set this value correctly within 32-bit boundary(frames).

Prev-Change-Id: I537a04156699d90549a0a468ae19539ecd552d3b
CRs-Fixed: 483203
Signed-off-by: Laxminath Kasam <lkasam@codeaurora.org>

Change-Id: Ife1e9debfce7cc62c88ca9587006f0e4e44a7a64