net: arc: select CRC32

Fix the following build/link error by adding a dependency on the CRC32
routines:

  ld: drivers/net/ethernet/arc/emac_main.o: in function `arc_emac_set_rx_mode':
  emac_main.c:(.text+0xb11): undefined reference to `crc32_le'

The crc32_le() call comes through the ether_crc_le() call in
arc_emac_set_rx_mode().

[v2: moved the select to ARC_EMAC_CORE; the Makefile is a bit confusing,
but the error comes from emac_main.o, which is part of the arc_emac module,
which in turn is enabled by CONFIG_ARC_EMAC_CORE. Note that arc_emac is
different from emac_arc...]

Fixes: 775dd682 ("arc_emac: implement promiscuous mode and multicast filtering")
Cc: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Vegard Nossum <vegard.nossum@oracle.com>
Link: https://lore.kernel.org/r/20211012093446.1575-1-vegard.nossum@oracle.comSigned-off-by: Jakub Kicinski <kuba@kernel.org>

drivers/net/ethernet/arc/Kconfig

@@ -21,6 +21,7 @@ config ARC_EMAC_CORE
 	depends on ARC || ARCH_ROCKCHIP || COMPILE_TEST
 	select MII
 	select PHYLIB
+	select CRC32
 
 config ARC_EMAC
 	tristate "ARC EMAC support"