iwmc3200wifi: Add a last_fw_err debugfs entry

In order to check what was the last fw error we got accross resets, we add
this debugfs entry. It displays the complete ASSERT information.

Signed-off-by: Samuel Ortiz <sameo@linux.intel.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>
diff --git a/drivers/net/wireless/iwmc3200wifi/rx.c b/drivers/net/wireless/iwmc3200wifi/rx.c
index 14950b1..40dbcbc 100644
--- a/drivers/net/wireless/iwmc3200wifi/rx.c
+++ b/drivers/net/wireless/iwmc3200wifi/rx.c
@@ -102,6 +102,8 @@
 	error = (struct iwm_umac_notif_error *)buf;
 	fw_err = &error->err;
 
+	memcpy(iwm->last_fw_err, fw_err, sizeof(struct iwm_fw_error_hdr));
+
 	IWM_ERR(iwm, "%cMAC FW ERROR:\n",
 	 (le32_to_cpu(fw_err->category) == UMAC_SYS_ERR_CAT_LMAC) ? 'L' : 'U');
 	IWM_ERR(iwm, "\tCategory:    %d\n", le32_to_cpu(fw_err->category));