net/fsl: xgmac_mdio: Add workaround for erratum A-009885

net/fsl: xgmac_mdio: Add workaround for erratum A-009885

commit 6198c722019774d38018457a8bfb9ba3ed8c931e upstream.

Once an MDIO read transaction is initiated, we must read back the data
register within 16 MDC cycles after the transaction completes. Outside
of this window, reads may return corrupt data.

Therefore, disable local interrupts in the critical section, to
maximize the probability that we can satisfy this requirement.

Fixes: d55ad2967d89 ("powerpc/mpc85xx: Create dts components for the FSL QorIQ DPAA FMan")
Signed-off-by: Tobias Waldekranz <tobias@waldekranz.com>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>