mvebu: remove default profile

mvebu: remove default profile

When using Image Builder and building image for Cortex A53 or
A72 subtargets, it'll fail with following message:

Collected errors:
 * opkg_install_cmd: Cannot install package mwlwifi-firmware-88w8864.
 * opkg_install_cmd: Cannot install package mwlwifi-firmware-88w8964.
make[2]: *** [Makefile:153: package_install] Error 255
make[1]: *** [Makefile:114: _call_image] Error 2

This is beacuse both packages are available only for Cortex A9 subtarget
and are included in PACKAGES array in default profile. Instead patching
this, let's remove profiles completely, since all necessary packages are
specified in DEVICE_PACKAGES array for each device.

Signed-off-by: Tomasz Maciej Nowak <tomek_n@o2.pl>