ACPI, APEI, ERST, Fix erst-dbg long record reading issue

When we debug ERST table with erst-dbg, if the error record in ERST
table is too long(>4K), it can't be read out.  So this patch increases
the buffer size to 16K to ensure such error records can be read from
ERST table.

Signed-off-by: Chen Gong <gong.chen@linux.intel.com>
Signed-off-by: Huang Ying <ying.huang@intel.com>
Signed-off-by: Len Brown <len.brown@intel.com>