drm/komeda: fix integer overflow in AFBC framebuffer size check

In the Linux kernel, the following vulnerability has been resolved:

drm/komeda: fix integer overflow in AFBC framebuffer size check

The AFBC framebuffer size validation calculates the minimum required buffer size by adding the AFBC payload size to the framebuffer offset. This addition is performed without checking for integer overflow.

If the addition oveflows, the size check may incorrectly succed and allow userspace to provide an undersized drm_gem_object, potentially leading to out-of-bounds memory access.

Add usage of check_add_overflow() to safely compute the minimum required size and reject the framebuffer if an overflow is detected. This makes the AFBC size validation more robust against malformed.

Found by Linux Verification Center (linuxtesting.org) with SVACE.