ARC: Fix malformed ARC_EMUL_UNALIGNED default

'default N' should be 'default n', though they happen to have the same
effect here, due to undefined symbols (N in this case) evaluating to n
in a tristate sense.

Remove the default from ARC_EMUL_UNALIGNED instead of changing it. bool
and tristate symbols implicitly default to n.

Discovered with the
https://urldefense.proofpoint.com/v2/url?u=https-3A__github.com_ulfalizer_Kconfiglib_blob_master_examples_list-5Fundefined.py&d=DwIBAg&c=DPL6_X_6JkXFx7AXWqB0tg&r=c14YS-cH-kdhTOW89KozFhBtBJgs1zXscZojEZQ0THs&m=WxxD8ozR7QQUVzNCBksiznaisBGO_crN7PBOvAoju8s&s=1LmxsNqxwT-7wcInVpZ6Z1J27duZKSoyKxHIJclXU_M&e=


script.

Signed-off-by: Ulf Magnusson <ulfalizer@gmail.com>
Signed-off-by: Vineet Gupta <vgupta@synopsys.com>