zink: handle non-const offsets for txf/tg4 ops
required for gl_spirv handling and tg4
Fixes: b77f43f2 ("zink: use ConstOffset for nir_tex_src_offset")
required for gl_spirv handling and tg4
Fixes: b77f43f2 ("zink: use ConstOffset for nir_tex_src_offset")