arm64: dts: ti: k3-am69-sk: Fix main_i2c0 alias

arm64: dts: ti: k3-am69-sk: Fix main_i2c0 alias

main_i2c0 is aliased as i2c0 which creates a problem for u-boot R5
SPL attempting to reuse the same definition in the common board
detection logic as it looks for the first i2c instance as the bus on
which to detect the eeprom to understand the board variant involved.
Switch main_i2c0 to i2c3 alias allowing us to introduce wkup_i2c0
and potentially space for mcu_i2c instances in the gap for follow on
patches.

Fixes: 635fb18ba008 ("arch: arm64: dts: Add support for AM69 Starter Kit")
Signed-off-by: Nishanth Menon <nm@ti.com>
Reviewed-by: Udit Kumar <u-kumar1@ti.com>
Link: https://lore.kernel.org/r/20230602214937.2349545-5-nm@ti.com
Signed-off-by: Vignesh Raghavendra <vigneshr@ti.com>