remoteproc: use SIZE_MAX in rproc_u64_fit_in_size_t()

remoteproc: use SIZE_MAX in rproc_u64_fit_in_size_t()

Smatch reports:

drivers/remoteproc/remoteproc_elf_loader.c:221
warn: always true condition '(val <= -1)'

The helper function rproc_u64_fit_in_size_t() compares the value
against (size_t)-1, which is equivalent to SIZE_MAX but can confuse
static analysis tools and lead to the above warning.

Replace (size_t)-1 with SIZE_MAX to make the intent explicit and
avoid the Smatch warning without changing the behavior.

Signed-off-by: Anas Iqbal <mohd.abd.6602@gmail.com>
Link: https://lore.kernel.org/r/20260314110137.178981-1-mohd.abd.6602@gmail.com
Signed-off-by: Mathieu Poirier <mathieu.poirier@linaro.org>