media: mtk-vpu: fix two smatch warnings

Drop the "id >= 0" test in two conditions to fix these warnings:

drivers/media/platform/mtk-vpu/mtk_vpu.c:276 vpu_ipi_register() warn: always true condition '(id >= 0) => (0-u32max >= 0)'
drivers/media/platform/mtk-vpu/mtk_vpu.c:401 vpu_wdt_reg_handler() warn: always true condition '(id >= 0) => (0-u32max >= 0)'

Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>