staging/csr: Fix dereference before check

Smatch complains about some pointers that are dereferenced before being
checked:

drivers/staging/csr/sme_sys.c:285
CsrWifiRouterCtrlHipReqHandler() warn: variable dereferenced before
check 'priv' (see line 283)
drivers/staging/csr/sme_sys.c:1503
CsrWifiRouterMaPacketReqHandler() warn: variable dereferenced before
check 'priv' (see line 1501)
drivers/staging/csr/sme_sys.c:2062
CsrWifiRouterCtrlPeerDelReqHandler() warn: variable dereferenced before
check 'priv' (see line 2059)
drivers/staging/csr/sme_sys.c:2477
CsrWifiRouterCtrlPeerAddReqHandler() warn: variable dereferenced before
check 'priv' (see line 2474)
drivers/staging/csr/sme_sys.c:3045
CsrWifiRouterCtrlWapiRxPktReqHandler() warn: variable dereferenced
before check 'priv' (see line 3039)

We put the check before the dereferencing and prevent an oops and fix
the warning.

Signed-off-by: Peter Huewe <peterhuewe@gmx.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>