Merge branch 'bugfix/btdm_iphone10_0_2' into 'master'

Bugfix/btdm iphone10 0 2

This connection error caused by iPhone, it think that TX data length must large than 27 when slave support EXTEND_DATA_LENGTH. But this should be allow. Besides,  the problem cannot be found on higher version of Iphone7, apple seemed to have fixed it.
Actually maybe other BLE device have the same problem.

See merge request !509