Fixes gcc '-Wunused-but-set-variable' warning:

drivers/net/ethernet/marvell/octeontx2/af/rvu.c: In function 'rvu_detach_rsrcs':
drivers/net/ethernet/marvell/octeontx2/af/rvu.c:855:6: warning:
 variable 'devnum' set but not used [-Wunused-but-set-variable]

drivers/net/ethernet/marvell/octeontx2/af/rvu.c:853:7: warning:
 variable 'is_pf' set but not used [-Wunused-but-set-variable]

drivers/net/ethernet/marvell/octeontx2/af/rvu.c: In function 'rvu_mbox_handler_ATTACH_RESOURCES':
drivers/net/ethernet/marvell/octeontx2/af/rvu.c:1054:7: warning:
 variable 'is_pf' set but not used [-Wunused-but-set-variable]

drivers/net/ethernet/marvell/octeontx2/af/rvu.c:1053:6: warning:
 variable 'devnum' set but not used [-Wunused-but-set-variable]

It never used since introduction in commit
746ea742 ("octeontx2-af: Add RVU block LF provisioning support")
Signed-off-by: NYueHaibing <yuehaibing@huawei.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>