net: atmel_macb Kconfig: remove long dependency line

Many Atmel SOC are embedding a MACB controller. This patch removes the long
dependency line for this Atmel MACB ethernet driver configuration entry.
The HAVE_NET_MACB configuration option is located in the net Kconfig file
as it may be setup by ARM/AT91 and AVR32 chips.

Signed-off-by: Jean-Christophe PLAGNIOL-VILLARD <plagnioj@jcrosoft.com>
Cc: David Miller <davem@davemloft.net>
Cc: Haavard Skinnemoen <hskinnemoen@atmel.com>
Acked-by: Nicolas Ferre <nicolas.ferre@atmel.com>
Acked-by: Andrew Victor <linux@maxim.org.za>