sfc: add CONFIG_INET dependency for TC offload

The driver now fails to link when CONFIG_INET is disabled, so
add an explicit Kconfig dependency:

ld.lld: error: undefined symbol: ip_route_output_flow
>>> referenced by tc_encap_actions.c
>>> drivers/net/ethernet/sfc/tc_encap_actions.o:(efx_tc_flower_create_encap_md) in archive vmlinux.a

ld.lld: error: undefined symbol: ip_send_check
>>> referenced by tc_encap_actions.c
>>> drivers/net/ethernet/sfc/tc_encap_actions.o:(efx_gen_encap_header) in archive vmlinux.a
>>> referenced by tc_encap_actions.c
>>> drivers/net/ethernet/sfc/tc_encap_actions.o:(efx_gen_encap_header) in archive vmlinux.a

ld.lld: error: undefined symbol: arp_tbl
>>> referenced by tc_encap_actions.c
>>> drivers/net/ethernet/sfc/tc_encap_actions.o:(efx_tc_netevent_event) in archive vmlinux.a
>>> referenced by tc_encap_actions.c
>>> drivers/net/ethernet/sfc/tc_encap_actions.o:(efx_tc_netevent_event) in archive vmlinux.a

Fixes: a1e82162af0b8 ("sfc: generate encap headers for TC offload")
Reviewed-by: Edward Cree <[e-mail]>
Reviewed-by: Simon Horman <[e-mail]>
Closes: https://lore.kernel.org/oe-kbuild-all/[e-mail]/
Signed-off-by: Arnd Bergmann <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Jakub Kicinski <[e-mail]>

drivers/net/ethernet/sfc/Kconfig

···
 config SFC_SRIOV
 	bool "Solarflare SFC9100-family SR-IOV support"
 	depends on SFC && PCI_IOV
+	depends on INET
 	default y
 	help
 	  This enables support for the Single Root I/O Virtualization