BaseTools: Fix flexible PCD DEVICE_PATH parse issue

When the format of DEVICE_PATH have string, like as:
{DEVICE_PATH("BBS(1,"AB",0)")} have string "AB", will
get the wrong value.

Cc: Liming Gao <liming.gao@intel.com>
Cc: Yonghong Zhu <yonghong.zhu@intel.com>
Contributed-under: TianoCore Contribution Agreement 1.1
Signed-off-by: Yunhua Feng <yunhuax.feng@intel.com>
Reviewed-by: Yonghong Zhu <yonghong.zhu@intel.com>

BaseTools/Source/Python/Common/Misc.py

@@ -1603,7 +1603,8 @@ def ParseFieldValue (Value):
                 Value = (Value << 8) | ((ItemValue >> 8 * I) & 0xff)
         return Value, RetSize
     if Value.startswith('DEVICE_PATH(') and Value.endswith(')'):
-        Value = Value.split('"')[1]
+        Value = Value.replace("DEVICE_PATH(", '').rstrip(')')
+        Value = Value.strip().strip('"')
         return ParseDevPathValue(Value)
     if Value.lower().startswith('0x'):
         Value = int(Value, 16)