nvir/nvc0: Align the user input size to 0x4
This is similar to what is done for NV50, and prevents from running into
“PUSH_NOT_ENOUGH_DATA” when the array is not aligned; as both the byte
size and the size in 32-bit words are uploaded, the hardware would
detect that the size in 32-bit words was less than expected if the size
was not aligned to 4-bytes first.