net: stmmac: replace has_xxxx with core_type

net: stmmac: replace has_xxxx with core_type

Replace the has_gmac, has_gmac4 and has_xgmac ints, of which only one
can be set when matching a core to its driver backend, with an
enumerated type carrying the DWMAC core type.

Tested-by: Maxime Chevallier <maxime.chevallier@bootlin.com>
Signed-off-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk>
Acked-by: Chen-Yu Tsai <wens@kernel.org>
Reviewed-by: Maxime Chevallier <maxime.chevallier@bootlin.com>
Tested-by: Mohd Ayaan Anwar <mohd.anwar@oss.qualcomm.com>
Reviewed-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>
Link: https://patch.msgid.link/E1vB6ld-0000000BIPy-2Qi4@rmk-PC.armlinux.org.uk
Signed-off-by: Jakub Kicinski <kuba@kernel.org>