drm/amd/amdkfd: Fix large framesize for kfd_smi_ev_read()

The buffer allocated is of 1024 bytes. Allocate this from
heap instead of stack.

Also remove check for stack size since we're allocating from heap

Signed-off-by: Aurabindo Pillai <aurabindo.pillai@amd.com>
Tested-by: Amber Lin <Amber.Lin@amd.com>
Reviewed-by: Felix Kuehling <Felix.Kuehling@amd.com>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>