main: consider that unsized arrays have at least one active element

main: consider that unsized arrays have at least one active element

From ARB_shader_storage_buffer_object:

"When using the ARB_program_interface_query extension to enumerate the
 set of active buffer variables, only the first element of arrays (sized
 or unsized) will be enumerated"

_mesa_program_resource_array_size() is used when getting the name (and
name length) of the active variables. When it is an unsized array,
we want to indicate it has one active element so the returned name
would have "[0]" at the end.

v2:
- Use array_stride > 0 and array_elements == 0 to detect unsized
  arrays. Because of that, we don't need is_unsized_array flag
  (Timothy)

Signed-off-by: Samuel Iglesias Gonsalvez <siglesias@igalia.com>
Reviewed-by: Timothy Arceri <t_arceri@yahoo.com.au>