main: fix GL_MAX_NUM_ACTIVE_VARIABLES value for shader storage blocks

main: fix GL_MAX_NUM_ACTIVE_VARIABLES value for shader storage blocks

The maximum number of active variables for shader storage blocks should
take into account the specific rules for shader storage blocks, i.e. for
an active shader storage block member declared as an array, an entry
will be generated only for the first array element, regardless of its type.

Fixes 3 dEQP-GLES31.functional.* tests:

dEQP-GLES31.functional.program_interface_query.shader_storage_block.active_variables.named_block
dEQP-GLES31.functional.program_interface_query.shader_storage_block.active_variables.unnamed_block
dEQP-GLES31.functional.program_interface_query.shader_storage_block.active_variables.block_array

Signed-off-by: Samuel Iglesias Gonsalvez <siglesias@igalia.com>
Reviewed-by: Tapani Pälli <tapani.palli@intel.com>