powerpc: dts: t1040rdb: fix compatible string for Rev A boards

powerpc: dts: t1040rdb: fix compatible string for Rev A boards

[ Upstream commit f5f84aea1202d72d999354221dea6e7a4026bb7d ]

It looks like U-Boot fails to start the kernel properly when the
compatible string of the board isn't fsl,T1040RDB, so stop overriding it
from the rev-a.dts.

Fixes: bd04d92fe8a1 ("powerpc: dts: t1040rdb: fix ports names for Seville Ethernet switch")
Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>