ARC: AXS10x: cleanup kconfig

As we've dropped NAND support for AXS101 and AXS103
see commit 4f5e552d ("ARC: AXS10x: drop NAND support")
we don't need bounce buffer anymore.

Signed-off-by: Eugeniy Paltsev <Eugeniy.Paltsev@synopsys.com>
Signed-off-by: Alexey Brodkin <abrodkin@synopsys.com>