libflash/mbox-flash: Add v2 error codes
#define MBOX_R_WRITE_ERROR 0x03
#define MBOX_R_SYSTEM_ERROR 0x04
#define MBOX_R_TIMEOUT 0x05
+#define MBOX_R_BUSY 0x06
+#define MBOX_R_WINDOW_ERROR 0x07
+#define MBOX_R_SEQ_ERROR 0x08
#define MBOX_ATTN_ACK_MASK 0x3
#define MBOX_ATTN_BMC_REBOOT (1 << 0)
