selftest: net: Fix weird setsockopt() in bind_bhash.c.

selftest: net: Fix weird setsockopt() in bind_bhash.c.

bind_bhash.c passes (SO_REUSEADDR | SO_REUSEPORT) to setsockopt().

In the asm-generic definition, the value happens to match with the
bare SO_REUSEPORT, (2 | 15) == 15, but not on some arch.

arch/alpha/include/uapi/asm/socket.h:18:#define SO_REUSEADDR	0x0004
arch/alpha/include/uapi/asm/socket.h:24:#define SO_REUSEPORT	0x0200
arch/mips/include/uapi/asm/socket.h:24:#define SO_REUSEADDR	0x0004	/* Allow reuse of local addresses.  */
arch/mips/include/uapi/asm/socket.h:33:#define SO_REUSEPORT 0x0200	/* Allow local address and port reuse.  */
arch/parisc/include/uapi/asm/socket.h:12:#define SO_REUSEADDR	0x0004
arch/parisc/include/uapi/asm/socket.h:18:#define SO_REUSEPORT	0x0200
arch/sparc/include/uapi/asm/socket.h:13:#define SO_REUSEADDR	0x0004
arch/sparc/include/uapi/asm/socket.h:20:#define SO_REUSEPORT	0x0200
include/uapi/asm-generic/socket.h:12:#define SO_REUSEADDR	2
include/uapi/asm-generic/socket.h:27:#define SO_REUSEPORT	15

Let's pass SO_REUSEPORT only.

Fixes: c35ecb95c448 ("selftests/net: Add test for timing a bind request to a port with a populated bhash entry")
Signed-off-by: Kuniyuki Iwashima <kuniyu@google.com>
Reviewed-by: Simon Horman <horms@kernel.org>
Link: https://patch.msgid.link/20250903222938.2601522-1-kuniyu@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>