[FIX] Fix PReq frame size check

Remove frame format error post if the received PReq frame is larger than
set in objetc 0x1F98.4 (PreqActPayloadLimit). Instead the PReq payload
size is compared with the configured limit.
This fixes issues with MNs that transmit larger PReq frames than
necessary.

Change-Id: I2be2d49d885e05e6104cb99fd0eedc55cfc63206
Reviewed-on: http://brateggevoat1/gerrit/2103
Tested-by: Jenkins <jenkins@brateggevoat1.br-automation.co.at>
Reviewed-by: Thomas Mair <thomas.mair@br-automation.com>
Reviewed-by: Josef Baumgartner <josef.baumgartner@br-automation.com>
[FIX] Fix Check Frame function in dllk

The function dllk_checkFrame checks the frame size before it actually
accesses the memory.

Resolves: #254

Change-Id: Ie0030109b8b8b9ca5dc7a9f4f74e41ed3516d90f
Reviewed-on: http://brateggevoat1/gerrit/2109
Tested-by: Jenkins <jenkins@brateggevoat1.br-automation.co.at>
Reviewed-by: Josef Baumgartner <josef.baumgartner@br-automation.com>
Reviewed-by: Joerg Zelenka <joerg.zelenka@br-automation.com>