u_format: Add restrict to fn pointer and manual format pack/unpack/fetch

u_format: Add restrict to fn pointer and manual format pack/unpack/fetch

MSVC warns (loudly) about a mismatch between the generated functions in
u_format_table.c and the definition of util_format_[un]pack_description,
specifically having 'restrict' in the function but not in the pointer
type in the struct.

So, add 'restrict' everywhere - to the function types, and to the rest
of the implementations that are assigned to those structs.

v2: util_format_unpack_description is used in gallium/auxiliary/translate

Fixes: 5785fdac ("u_format: Mark the generated pack/unpack src/dst args as restrict.")
Reviewed-by: Eric Anholt <eric@anholt.net>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/9670>