dts: imx8qxp-mek: Add PHY post reset delay

PHY cannot be detected unless we wait about 150 ms.

Signed-off-by: Andrejs Cainikovs <andrejs.cainikovs@netmodule.com>
Reviewed-by: Anatolij Gustschin <agust@denx.de>
Reviewed-by: Stefano Babic <sbabic@denx.de>
Acked-by: Joe Hershberger <joe.hershberger@ni.com>