arm64: dts: agilex/stratix10/n5x: fix dtbs_check for rstmgr

The bindings expect "altr,rst-mgr" as a fallback in the rstmgr
compatible:

rstmgr@ffd11000: compatible: 'oneOf' conditional failed, one must be fixed:
        ['altr,stratix10-rst-mgr'] is too short
        'altr,rst-mgr' was expected

Signed-off-by: Dinh Nguyen <dinguyen@kernel.org>