turnip: fix invalid VK_ERROR_OUT_OF_POOL_MEMORY

turnip: fix invalid VK_ERROR_OUT_OF_POOL_MEMORY

When VK_DESCRIPTOR_TYPE_SAMPLER is provided, it doesn't need to be
counted as a buffer count. Otherwise it leads to mismatch of allocated
buffer size, hitting VK_ERROR_OUT_OF_POOL_MEMORY finally.

Fixes: c39afe68f0390d45130c1317b3b7e65f55542c36
Also fixes amber tests:
./tests/cases/address_modes_float.amber
./tests/cases/address_modes_int.amber
./tests/cases/magfilter_linear.amber
./tests/cases/magfilter_nearest.amber

Reviewed-by: Jonathan Marek <jonathan@marek.ca>