tools/nolibc/select: avoid libgcc 64-bit multiplications

tools/nolibc/select: avoid libgcc 64-bit multiplications

timeval::tv_usec is going to be 64-bit wide even on 32-bit
architectures. As not all architectures support 64-bit multiplications
instructions, calls to libgcc (__multi3()) may be emitted by the
compiler which are not provided by nolibc.

As tv_usec and tv_nsec are guaranteed to always fit into an uint32_t,
perform a 32-bit multiplication instead.

Signed-off-by: Thomas Weißschuh <linux@weissschuh.net>
Acked-by: Willy Tarreau <w@1wt.eu>
Reviewed-by: Arnd Bergmann <arnd@arndb.de>
Link: https://patch.msgid.link/20251220-nolibc-uapi-types-v3-7-c662992f75d7@weissschuh.net