drm/amdgpu: bail out when failed to load fw in psp_init_cap_microcode()

In function psp_init_cap_microcode(), it should bail out when failed to
load firmware, otherwise it may cause invalid memory access.

Fixes: 07dbfc6b ("drm/amd: Use `amdgpu_ucode_*` helpers for PSP")
Reviewed-by: Lijo Lazar <lijo.lazar@amd.com>
Signed-off-by: Jiang Liu <gerry@linux.alibaba.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>