ARM: at91/defconfig: remove useless configuration in at91sam9260_9g20_defconfig

A few configuration symbols are deprecated and disappeared a few versions ago,
remove them.

CONFIG_FPE_NWFPE depends on OABI_COMPAT which was not selected.

Signed-off-by: Alexandre Belloni <alexandre.belloni@free-electrons.com>
Signed-off-by: Nicolas Ferre <nicolas.ferre@atmel.com>