ar71xx: add support for dlink dir-615-e1

Dlink dir-615-e1 can use dir-600-a1's image, but the factory
firmware's partition of dir-615-e1 is not equal to dir-600-a1's
openwrt image, and also dir-600-a1's image can't be uploaded through
dlink's normal firmware update web page(by changing the last bytes of
dir-600-a1's image, it can be uploaded through dlink's failsafe mode
uboot web page, but it's not compatible with modern browsers, see
[1]).

Add profile to dir-615-e1 so the generated image's partition is equal
to factory firmware's(by calling CameoAP99 in SingleProfile), and so
the image can be uploaded through the normal firmware update web
page(surely it also can be uploaded through dlink's failsafe mode
uboot web page :-) ).

This address ticket #8680.

[1]: http://wiki.openwrt.org/toh/d-link/dir-615#browser.issues
ar71xx: image: clean up and add missing argument for some macros

Macro Sysupgrade/KR is not used and seems unnecessary, so remove
it. Also add padding argument to macro Sysupgrade/RKuImage.
base-files: remove function service_kill

Function service_kill is deprecated and has no user, so remove it.
package: netifd: remove blank line at the end of file