Fix `VK_NULL_HANDLE` comparison style (#5733)

Summary:
Pull Request resolved: https://github.com/pytorch/executorch/pull/5733

`VK_NULL_HANDLE` is a constant and should hence be the right hand side of the expression. Fixing the expressions where it's on the left hand side.
ghstack-source-id: 245169615
exported-using-ghexport

Reviewed By: nathanaelsee

Differential Revision: D63560116

fbshipit-source-id: a0b03202245988c7c072002c26e430f80436992b