glsl: join calculate_array_size() and calculate_array_stride()

glsl: join calculate_array_size() and calculate_array_stride()

These helpers are ran for same case the same loop. Here joined
their operation so the loop is ran just once. Also fixed
out-of-memory condition here.

v2: Make the loop simpler to read as per Tapani's suggestion

Signed-off-by: Juha-Pekka Heikkila <juhapekka.heikkila@gmail.com>
Reviewed-by: Samuel Iglesias Gonsálvez <siglesias@igalia.com>
Tested-by: Tapani Pälli <tapani.palli@intel.com>