ARM: always enable AEABI for ARMv6+

Always enable AEABI for ARMv6+, as these use the double-word exclusives
which must be passed an even register to avoid errors such as:

/tmp/ccG2rCwe.s:905: Error: even register required -- `ldrexd r5,r6,[r7]'
/tmp/ccG2rCwe.s:909: Error: even register required -- `strexd sl,r3,r4,[r7]'

Signed-off-by: Russell King <rmk+kernel@armlinux.org.uk>