ARM: dts: imx7-mba7: Remove duplicated power supply

ARM: dts: imx7-mba7: Remove duplicated power supply

VCC3V3 is used twice, resulting in the debugfs warning:
debugfs: Directory 'VCC3V3' with parent 'regulator' already present!

The power supply provided by reg_vcc_3v3 is actually the same as
reg_mba_3v3.

Signed-off-by: Alexander Stein <alexander.stein@ew.tq-group.com>
Reviewed-by: Markus Niebel <markus.niebel@ew.tq-group.com>
Reviewed-by: Bruno Thomsen <bruno.thomsen@gmail.com>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>