media: venus: hfi_parser: Check for instance after hfi platform get

The inst function argument is != NULL only for Venus v1 and
we did not migrate v1 to a hfi_platform abstraction yet. So
check for instance != NULL only after hfi_platform_get returns
no error.

Fixes: e2992926 ("media: venus: Get codecs and capabilities from hfi platform")
Cc: stable@vger.kernel.org # v5.12
Signed-off-by: Stanimir Varbanov <stanimir.varbanov@linaro.org>
Tested-by: Bryan O'Donoghue <bryan.odonoghue@linaro.org>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>