Increase size of default printk buffer in error logs

Recent changes to add more data to our exception path have made
the printk output we get in our error logs less useful than it
should be.  It currently takes at minimum 1076 bytes for a single
exception.  That number would increase if the backtrace got very
large.  This change resizes the buffer to allow for 17 stack
frames within a single exception (1280 bytes).

Change-Id: I029283ee39877c3ace812fd85c0fbc26cdecf230
Reviewed-on: http://rchgit01.rchland.ibm.com/gerrit1/86596
Tested-by: Jenkins Server <pfd-jenkins+hostboot@us.ibm.com>
Tested-by: Jenkins OP Build CI <op-jenkins+hostboot@us.ibm.com>
Tested-by: Jenkins OP HW <op-hw-jenkins+hostboot@us.ibm.com>
Tested-by: FSP CI Jenkins <fsp-CI-jenkins+hostboot@us.ibm.com>
Reviewed-by: Matt Derksen <mderkse1@us.ibm.com>
Reviewed-by: Zachary Clark <zach@ibm.com>
Reviewed-by: Nicholas E Bofferding <bofferdn@us.ibm.com>

src/include/usr/errl/errludprintk.H

@@ -5,7 +5,9 @@
 /*                                                                        */
 /* OpenPOWER HostBoot Project                                             */
 /*                                                                        */
-/* COPYRIGHT International Business Machines Corp. 2014                   */
+/* Contributors Listed Below - COPYRIGHT 2014,2019                        */
+/* [+] International Business Machines Corp.                              */
+/*                                                                        */
 /*                                                                        */
 /* Licensed under the Apache License, Version 2.0 (the "License");        */
 /* you may not use this file except in compliance with the License.       */
@@ -39,7 +41,7 @@ namespace ERRORLOG
     class ErrlUserDetailsPrintk : public ErrlUserDetails
     {
         public:
-            enum { DEFAULT_SIZE_BYTES = 256 };
+            enum { DEFAULT_SIZE_BYTES = 1280 };
 
             /** @brief Constructor
              *