meson: Use consistent style

Currently the meosn build has a mix of two styles:
arg : [foo, ...
       bar],

and
arg : [
  foo, ...,
  bar,
]

For consistency let's pick one. I've picked the later style, which I
think is more readable, and is more common in the mesa code base.

v2: - fix commit message

Acked-by: Eric Engestrom <eric.engestrom@imgtec.com>
Signed-off-by: Dylan Baker <dylan.c.baker@intel.com>