ARM: dts: Fix wrong clocks for dra7 mcasp

The ahclkr clkctrl clock bit 28 only exists for mcasp 1 and 2 on dra7.
This causes the following warning on beagle-x15:

ti-sysc 48468000.target-module: could not add child clock ahclkr: -19

Also the mcasp clkctrl clock bits are wrong:

For mcasp1 and 2 we have four clocks at bits 28, 24, 22 and 0:

bit 28 is ahclkr
bit 24 is ahclkx
bit 22 is auxclk
bit 0 is fck

For mcasp3 to 8 we have three clocks at bits 24, 22 and 0.

bit 24 is ahclkx
bit 22 is auxclk
bit 0 is fck

We do not have currently mapped auxclk at bit 22 for the drivers, that can
be added if needed.

Fixes: 5241ccbf

 ("ARM: dts: Add missing ranges for dra7 mcasp l3 ports")
Cc: Suman Anna <s-anna@ti.com>
Cc: Tero Kristo <t-kristo@ti.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>