sunxi: Remove board defconfig-s for specific Q8 tablet PCB-s

sunxi: Remove board defconfig-s for specific Q8 tablet PCB-s

We now have generic q8_a?3_defconfig files for Q8 formfactor tablets with
an A13 / A23 / A33 SoC, there is no need for these PCB variant specific
defconfig-s and they only serve to confuse the user.

Note that in case of the forfun_q88db_defconfig and TZX-Q8-713B7_defconfig
for A13 based Q8 tablets there is not even a dts file for these in the
upstream kernel, which is all the more reason to remove them.

The generic q8_a?3_defconfig files have been tested on an Et_q8_v1_6,
Ippo_q8h_v1_2_a33_1024x600, Ippo_q8h_v1_2 and TZX-Q8-713B7 tablet, and the
forfun_q88db_defconfig is identical to q8_a13_tablet_defconfig.

This leaves only the Ippo_q8h_v5 untested with the new generic defconfigs
but there is no reason to assume that it will not work.

Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Acked-by: Ian Campbell <ijc@hellion.org.uk>