[phantom] Skip command PEG initialisation if PEG is already running

It is possible for the BIOS to use the UNDI API to bring up the NIC
prior to system boot.  If this happens, UNM_NIC_REG_CMDPEG_STATE will
contain the value 0xf00f (UNM_NIC_REG_CMDPEG_STATE_INITIALIZE_ACK),
and we should skip initialising the command PEG.

src/drivers/net/phantom/phantom.c

@@ -1673,6 +1673,17 @@ static int phantom_init_cmdpeg ( struct phantom_nic *phantom ) {
 	uint32_t cmdpeg_state;
 	uint32_t last_cmdpeg_state = 0;
 
+	/* Check for a previous initialisation.  This could have
+	 * happened if, for example, the BIOS used the UNDI API to
+	 * drive the NIC prior to a full PXE boot.
+	 */
+	cmdpeg_state = phantom_readl ( phantom, UNM_NIC_REG_CMDPEG_STATE );
+	if ( cmdpeg_state == UNM_NIC_REG_CMDPEG_STATE_INITIALIZE_ACK ) {
+		DBGC ( phantom, "Phantom %p command PEG already initialized\n",
+		       phantom );
+		return 0;
+	}
+
 	/* If this was a cold boot, check that the hardware came up ok */
 	cold_boot = phantom_readl ( phantom, UNM_CAM_RAM_COLD_BOOT );
 	if ( cold_boot == UNM_CAM_RAM_COLD_BOOT_MAGIC ) {