tools/nolibc/select: drop non-pselect based implementations

tools/nolibc/select: drop non-pselect based implementations

These implementations use the libc 'struct timeval' with system calls
which can lead to type mismatches. Currently this is fine, but will
break with upcoming changes to 'struct timeval'.

If the structure needs to be converted anyways, the implementations
based on pselect can be used for all architectures. This simplifies the
logic.

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-v3-3-c662992f75d7@weissschuh.net