Use hardware i2c adapter instead of PL via AXI

Requires design change:
- Remove AXI IIC controller
- Enable i2c0 in PS, connect to EMIO
- Connect ps i2c to the i2c mixer in PL
Adjust IRQ numbers for I2S DMA periferal

Apparently they moved to 87/88 (add "32" to get the DTS value) instead
of 86/87.
zynq-zc702-adv7511.dts: Fix HDMI audio DMA channel

DTS was still using old syntax, this fixes the HDMI audio failing
with EINVAL on any attempt to playback audio.
zynq-zed.dtsi: Reduce SD clock frequency from 50 to 33 MHz.

Zedboard often failed to boot as a result of the SD frequency being
too high. Add a label to the sdcard interface and override its
frequency in zynq-zed.dtsi.
Merge branch 'zed_hard_i2c_experiment' into xcomm_zynq