[RXRPC]: Remove Makefile reference to obsolete RXRPC config variable

Since there is no Kconfig variable RXRPC anywhere in the tree, and the
variable AF_RXRPC performs exactly the same function, remove the
reference to CONFIG_RXRPC from net/Makefile.
Signed-off-by: Robert P. J. Day <rpjday@mindspring.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/Makefile

@@ -37,7 +37,6 @@ obj-$(CONFIG_AX25)		+= ax25/
 obj-$(CONFIG_IRDA)		+= irda/
 obj-$(CONFIG_BT)		+= bluetooth/
 obj-$(CONFIG_SUNRPC)		+= sunrpc/
-obj-$(CONFIG_RXRPC)		+= rxrpc/
 obj-$(CONFIG_AF_RXRPC)		+= rxrpc/
 obj-$(CONFIG_ATM)		+= atm/
 obj-$(CONFIG_DECNET)		+= decnet/