remoteproc: k3-r5: cast size to size_t6dd

remoteproc: k3-r5: cast size to size_t6dd

When compiling for R5 core with CONFIG_REMOTEPROC_TI_K3_R5F,
passing 'size' (ulong) to ti_secure_image_post_process() caused
a type mismatch compiler error.

On platforms where ulong and size_t differ in size, directly
casting could lead to out-of-bounds memory access. Fix by
introducing a size_t temporary variable, passing it to the
function, and writing back the potentially modified value for
use in subsequent calls.

Signed-off-by: Philippe Schenker <philippe.schenker@impulsing.ch>
Acked-by: Andrew Davis <afd@ti.com>