nvk: bump NVK_PUSH_MAX_SYNCS to 256
What does this MR do and why?
nvk: bump NVK_PUSH_MAX_SYNCS to 256
technically this needs to be MUCH higher since there's no limitation
on the number of semaphore waits that can be submitted, but this is
enough to handle zink usage
fixes KHR-GL46.sparse_buffer_tests.BufferStorageTest
cc: mesa-stable