Fix one character displacement for cursor in line edits

Fix one character displacement for cursor in line edits

The variable m_inlinePosition was not updated when m_preeditString
was cleared in QCoeFepInputContext. This resulted in cursor displaying
up one character beyond where it logically should have been when
using HW Qwerty keyboard on E7 and similar devices.

Task-number: QTBUG-16238
Reviewed-by: axis
(cherry picked from commit 81351f2c6f9a939e4c34cb3be6280d396c21941f)