arm: dts: am33xx: Remove redundant interrupt-parent property

Interrupt-parent property is defined in the root node as
"interrupt-parent = <&intc>". This interrupt-parent value becomes
the default for the system, so removed redundant "interrupt-parent"
property from mmc, mac, lcdc and tscadc nodes.

Signed-off-by: Suniel Mahesh <sunil.m@techveda.org>
Signed-off-by: Tony Lindgren <tony@atomide.com>