hw/net: Add NPCMXXX GMAC device

This patch implements the basic registers of GMAC device and sets
registers for networking functionalities.

Tested:
The following message shows up with the change:
Broadcom BCM54612E stmmac-0:00: attached PHY driver [Broadcom BCM54612E] (mii_bus:phy_addr=stmmac-0:00, irq=POLL)
stmmaceth f0802000.eth eth0: Link is Up - 1Gbps/Full - flow control rx/tx

Change-Id: If71c6d486b95edcccba109ba454870714d7e0940
Signed-off-by: Hao Wu <wuhaotsh@google.com>
Signed-off-by: Nabih Estefan Diaz <nabihestefan@google.com>
Reviewed-by: Tyrone Ting <kfting@nuvoton.com>
Message-id: 20240110234232.4116804-5-nabihestefan@google.com
[PMM: Squashed another patch into this one to avoid compilation failure]
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>

hw/net/meson.build

@@ -38,7 +38,7 @@ system_ss.add(when: 'CONFIG_I82596_COMMON', if_true: files('i82596.c'))
 system_ss.add(when: 'CONFIG_SUNHME', if_true: files('sunhme.c'))
 system_ss.add(when: 'CONFIG_FTGMAC100', if_true: files('ftgmac100.c'))
 system_ss.add(when: 'CONFIG_SUNGEM', if_true: files('sungem.c'))
-system_ss.add(when: 'CONFIG_NPCM7XX', if_true: files('npcm7xx_emc.c'))
+system_ss.add(when: 'CONFIG_NPCM7XX', if_true: files('npcm7xx_emc.c', 'npcm_gmac.c'))
 
 system_ss.add(when: 'CONFIG_ETRAXFS', if_true: files('etraxfs_eth.c'))
 system_ss.add(when: 'CONFIG_COLDFIRE', if_true: files('mcf_fec.c'))