[SPIRV] fix several issues in builds with expensive checks

The patch fixes "Virtual register does not match instruction constraint"
and partly "Illegal virtual register for instruction" fails in the SPIRV
backend builds with LLVM_ENABLE_EXPENSIVE_CHECKS enabled. As a result,
the number of passed LIT tests with enabled checks is doubled.

Also, support for ndrange_*D builtins is placed in a separate function.

Differential Revision: https://reviews.llvm.org/D144897