ARM: dts: AM33XX: Fix uart numbering to match hardware/TRM

With DT support, where naming convention is based on base-addr
and not id, so we should follow TRM/Spec numbering label.

This patch changes UART numbering as per TRM, as uart0-5.

Signed-off-by: Vaibhav Hiremath <hvaibhav@ti.com>
Acked-by: Matt Porter <mporter@ti.com>
Cc: Peter Korsgaard <jacmet@sunsite.dk>
Signed-off-by: Benoit Cousson <benoit.cousson@linaro.org>