net: stmmac: Specify hardware capability value when FIFO size isn't specified

When Tx/Rx FIFO size is not specified in advance, the driver checks if
the value is zero and sets the hardware capability value in functions
where that value is used.

Consolidate the check and settings into function stmmac_hw_init() and
remove redundant other statements.

If FIFO size is zero and the hardware capability also doesn't have upper
limit values, return with an error message.

Signed-off-by: Kunihiko Hayashi <hayashi.kunihiko@socionext.com>
Reviewed-by: Yanteng Si <si.yanteng@linux.dev>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>