msm: kgsl: Add a property to find alignment of secure buffers

Add a property to determine the hardware alignment
constraint on allocation of secure buffers. XPUv2 and
below have a minimum requirement of 1 MBytes alignment
and hence driver should allocate memory with minimum
alignment on size.

Change-Id: Ie3ca5da489bc94ae57ddc6695e402463fd7a88c2
Signed-off-by: Sunil Khatri <sunilkh@codeaurora.org>