ARM: dts: imx6: phyFLEX: Fix UART hardware flow control

stable inclusion
from stable-5.10.53
commit d05ebeffca1d42734e012ede2fef5c5a76677224
bugzilla: 175574 https://gitee.com/openeuler/kernel/issues/I4DTUX

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=d05ebeffca1d42734e012ede2fef5c5a76677224



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[ Upstream commit 14cdc1f2 ]

Serial interface uart3 on phyFLEX board is capable of 5-wire connection
including signals RTS and CTS for hardware flow control.

Fix signals UART3_CTS_B and UART3_RTS_B padmux assignments and add
missing property "uart-has-rtscts" to allow serial interface to be
configured and used with the hardware flow control.

Signed-off-by: Primoz Fiser <primoz.fiser@norik.com>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Chen Jun <chenjun102@huawei.com>
Acked-by: Weilong Chen <chenweilong@huawei.com>
Signed-off-by: Chen Jun <chenjun102@huawei.com>
Signed-off-by: Zheng Zengkai <zhengzengkai@huawei.com>