staging: media: atomisp: use array3_size() for overflow-safe allocation

staging: media: atomisp: use array3_size() for overflow-safe allocation

Replace open-coded width * height * sizeof() multiplications with
array3_size() to prevent integer overflow in buffer allocations.

The atomisp driver computes DVS, morphing table, shading table and
statistics buffer sizes using unchecked arithmetic.  When dimensions
are attacker-controlled or simply large, the product can silently wrap,
causing kvmalloc() to allocate an undersized buffer.

array3_size() saturates to SIZE_MAX on overflow, so kvmalloc() returns
NULL instead of succeeding with too few bytes.

Signed-off-by: Feng Ning <feng@innora.ai>
Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>