include/uapi/linux/swab.h: move explicit cast outside ternary

include/uapi/linux/swab.h: move explicit cast outside ternary

A cast inside __builtin_constant_p doesn't do anything since it should
evaluate as constant at compile time irrespective of this cast.  Instead,
I moved this cast outside the ternary to ensure the return type is as
expected.

Additionally, if __HAVE_BUILTIN_BSWAP16__ was not defined then __swab16 is
actually returning an `int` not a `u16` due to integer promotion.

As Al Viro notes:
You *can't* get smaller-than-int out of ? :, same as you can't get it
out of addition, etc.

This also fixes some clang -Wformat warnings involving default
argument promotion.

Link: https://github.com/ClangBuiltLinux/linux/issues/378
Link: https://lkml.kernel.org/r/20220608223539.470472-1-justinstitt@google.com
Signed-off-by: Justin Stitt <jstitt007@gmail.com>
Suggested-by: Al Viro <viro@zeniv.linux.org.uk>
Suggested-by: Nathan Chancellor <nathan@kernel.org>
Reviewed-by: Nathan Chancellor <nathan@kernel.org>
Suggested-by: Nick Desaulniers <ndesaulniers@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>