[SPIR-V] Invalid SPIR-V when mutating struct using method and vk::BufferPointer

Description
Trying to mutate a struct using a method through a vk::BufferPointer causes invalid SPIR-V with non-aligned load ops to be generated.

Steps to Reproduce
https://godbolt.org/z/1vPTjjn6n

struct Foo {
    uint a;
    void increment() {
        a += 1;    
    }
};

[[vk::push_constant]]
struct Pc {
    vk::BufferPointer<Foo> ptr;
} pc;

[numthreads(1, 1, 1)]
void main() {
    pc.ptr.Get().increment();
}

Actual Behavior
fatal error: generated SPIR-V is invalid: [VUID-StandaloneSpirv-PhysicalStorageBuffer64-04708] Memory accesses with PhysicalStorageBuffer must use Aligned.
%20 = OpLoad %uint %19

Environment

• DXC trunk

Start by reproducing the HLSL example from the linked Godbolt case with DXC trunk and inspect the generated SPIR-V around the reported OpLoad. Use the PhysicalStorageBuffer64-04708 validation error as the completion criterion: the mutation through vk::BufferPointer should no longer generate invalid, non-aligned load operations.