ACPICA: Disassembler: Expand maximum output string length to 64K

Was 256 bytes max. The original purpose of this constraint was to
limit the amount of debug output. However, the string function in
question (UtPrintString) is now used for the disassembler also,
where 256 bytes is insufficient. Reported by RehabMan@GitHub.

Signed-off-by: Bob Moore <robert.moore@intel.com>
Signed-off-by: Lv Zheng <lv.zheng@intel.com>
Acked-by: Len Brown <len.brown@intel.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>