lima: fix allocation of GP outputs storage for indexed draw

lima: fix allocation of GP outputs storage for indexed draw

For indexed draw number of VS invocations is (ctx->max_index - ctx->min_index + 1),
so we have to use this number when calculating space for varyings, gl_Position and
gl_PointSize.

Fixes dEQP-GLES2.functional.buffer.write.use.index_array.array and
dEQP-GLES2.functional.buffer.write.use.index_array.element_array

Reviewed-by: Andreas Baierl <ichgeh@imkreisrum.de>
Reviewed-by: Erico Nunes <nunes.erico@gmail.com>
Signed-off-by: Vasily Khoruzhick <anarsoul@gmail.com>