ARC: [plat-axs*]: Enable SWAP

SWAP support on ARC was fixed earlier by
commit 6e376114 ("ARC: Fix CONFIG_SWAP")
so now we may safely enable it on platforms that
have external media like USB and SD-card.

Note: it was already allowed for HSDK

Signed-off-by: Alexey Brodkin <abrodkin@synopsys.com>
Cc: stable@vger.kernel.org # 6e376114: ARC: Fix CONFIG_SWAP
Signed-off-by: Vineet Gupta <vgupta@synopsys.com>