IB/rxe: Change RDMA_RXE kconfig to use select

NET_UDP_TUNNEL is not user selectable, so it should be used as a select
in kconfig.

CRYPTO_CRC32 is a required library for RDMA_RXE so it should active
automatically, as most other CRYPTO_ users do.
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>

drivers/infiniband/sw/rxe/Kconfig

 config RDMA_RXE
 	tristate "Software RDMA over Ethernet (RoCE) driver"
 	depends on INET && PCI && INFINIBAND
-	depends on NET_UDP_TUNNEL
-	depends on CRYPTO_CRC32
+	select NET_UDP_TUNNEL
+	select CRYPTO_CRC32
 	select DMA_VIRT_OPS
 	---help---
 	This driver implements the InfiniBand RDMA transport over