net: stmmac: replace the has_integrated_pcs field with a flag

struct plat_stmmacenet_data contains several boolean fields that could be
easily replaced with a common integer 'flags' bitfield and bit defines.

Start the process with the has_integrated_pcs field.

Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>
Reviewed-by: Andrew Halaney <ahalaney@redhat.com>
Link: https://lore.kernel.org/r/20230710090001.303225-2-brgl@bgdev.pl


Reviewed-by: Simon Horman <simon.horman@corigine.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>