drm/amd: fix some dead code in `gfx_v9_0_init_cp_compute_microcode`

Some dead code was introduced as part of utilizing the `amdgpu_ucode_*`
helpers. Adjust the control flow to make sure that firmware is released
in the appropriate error flows.

Reported-by: coverity-bot <keescook+coverity-bot@chromium.org>
Addresses-Coverity-ID: 1530548 ("Control flow issues")
Fixes: ec787deb ("drm/amd: Use `amdgpu_ucode_*` helpers for GFX9")
Signed-off-by: Mario Limonciello <mario.limonciello@amd.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>