[SPIR-V] Set non-kernel function linkage type via OpDecorate for all linkage types except for static functions

[VyacheslavLevytskyy]

Now SPIR-V Backend generates linkage type declaration via OpDecorate only for external and linkonce_odr linkage types. This makes it impossible to use, for example, extern_weak functions. The following example would crash:

define i32 @abs(i32 noundef %x) {
entry:
  %call = tail call spir_func i32 @__devicelib_abs(i32 noundef %x) #11
  ret i32 %call
}

declare extern_weak i32 @__devicelib_abs(i32 noundef)

We should fix the behaviour, probably in a way that corresponds to Khronos SPIRV Translator that sets non-kernel function linkage type via OpDecorate for all linkage types except for static functions.