media: ti-vpe: Fix a parallel build issue

When TI CAL was introduce as another driver under platform/ti-vpe
adding a second entry into the ti-vpe directory in the platform
Makefile caused issues during parallel build.

Signed-off-by: Benoit Parrot <bparrot@ti.com>
Signed-off-by: Jyri Sarha <jsarha@ti.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>