drm/radeon: fix integer overflow in radeon_align_pitch()

In the Linux kernel, the following vulnerability has been resolved: drm/radeon: fix integer overflow in radeon_align_pitch() radeon_align_pitch() has the same kind of overflow issue as the old amdgpu helper: both the alignment round-up add and the final 'aligned * cpp' calculation can overflow signed int. If that wraps, radeon_mode_dumb_create() can end up returning an invalid pitch or creating a zero-sized dumb buffer. Fix this by using check_add_overflow() for the alignment round-up and check_mul_overflow() for the final pitch calculation, returning 0 on overflow. Also reject zero pitch and size in radeon_mode_dumb_create(). Found via AST-based call-graph analysis using sqry.