overflow: Allow non-type arg to type_max() and type_min()

overflow: Allow non-type arg to type_max() and type_min()

A common use of type_max() is to find the max for the type of a
variable. Using the pattern type_max(typeof(var)) is needlessly
verbose. Instead, since typeof(type) == type we can just explicitly
call typeof() on the argument to type_max() and type_min(). Add
wrappers for readability.

We can do some replacements right away:

$ git grep '\btype_\(min\|max\)(typeof' | wc -l
11

Link: https://lore.kernel.org/r/20240301062221.work.840-kees@kernel.org
Signed-off-by: Kees Cook <keescook@chromium.org>