net: stmmac: remove unused duplicate property snps,axi_all

For core revision 3.x Address-Aligned Beats is available in two registers.
The DT property snps,aal was created for AAL in the DMA bus register,
which is a read/write bit.
The DT property snps,axi_all was created for AXI_AAL in the AXI bus mode
register, which is a read only bit that reflects the value of AAL in the
DMA bus register.

Since the value of snps,axi_all is never used in the driver,
and since the property was created for a bit that is read only,
it should be safe to remove the property.

Acked-by: Giuseppe Cavallaro <peppe.cavallaro@st.com>
Signed-off-by: Niklas Cassel <niklas.cassel@axis.com>
Signed-off-by: David S. Miller <davem@davemloft.net>