selinux: remove set but not used variable 'sidtab'

security/selinux/ss/services.c: In function security_port_sid:
security/selinux/ss/services.c:2346:17: warning: variable sidtab set but not used [-Wunused-but-set-variable]
security/selinux/ss/services.c: In function security_ib_endport_sid:
security/selinux/ss/services.c:2435:17: warning: variable sidtab set but not used [-Wunused-but-set-variable]
security/selinux/ss/services.c: In function security_netif_sid:
security/selinux/ss/services.c:2480:17: warning: variable sidtab set but not used [-Wunused-but-set-variable]
security/selinux/ss/services.c: In function security_fs_use:
security/selinux/ss/services.c:2831:17: warning: variable sidtab set but not used [-Wunused-but-set-variable]

Since commit 66f8e2f0 ("selinux: sidtab reverse lookup hash table")
'sidtab' is not used any more, so remove it.

Reported-by: Hulk Robot <hulkci@huawei.com>
Signed-off-by: YueHaibing <yuehaibing@huawei.com>
Signed-off-by: Paul Moore <paul@paul-moore.com>