Bluetooth: gatt: cancel all prepared writes on invalid write response

On sending write request we should check write response.
If data prepaired to be written by peer or offset are not equal
to the data and offset we sent, we shall send Execute Write
Request with Request Flag set to 0x00 (Cancel All Prepared Writes).

This was affecting GATT/CL/GAW/BI-32-C and GATT/CL/GAW/BI-37-C

Signed-off-by: Krzysztof Kopyściński <krzysztof.kopyscinski@codecoup.pl>