[NVPTX] Promote i24, i40, i48 and i56 to next power-of-two register when passing

Today llc will crash when attempting to use non-power-of-two integer types as
function arguments or returns. This patch enables passing non standard integer
values in functions by promoting them before store and truncating after load.

The main motivation of implementing this change is that rust casts small structs
(less than pointer size) into an integer of the same size. As an example, if a
struct contains three u8 then it will be passed as an i24. This patch is a step
towards enabling rust compilation to ptx while retaining the target independent
optimizations.

More context can be found in https://github.com/llvm/llvm-project/issues/55764

Differential Revision: https://reviews.llvm.org/D129291