Android: Fix compilation on official Qt5.1 SDK package

Compilation is terminated with errors:

In file included from E:\git\ng\123\qtserialport\src\serialport\qserialport.cpp:53:
E:\git\ng\123\qtserialport\src\serialport\/qserialport_unix_p.h:51:28: error: linux/serial.h: No such file or directory
In file included from E:\git\ng\123\qtserialport\src\serialport\qserialport.cpp:53:
E:\git\ng\123\qtserialport\src\serialport\/qserialport_unix_p.h:112: error: field 'currentSerialInfo' has incomplete type
E:\git\ng\123\qtserialport\src\serialport\/qserialport_unix_p.h:113: error: field 'restoredSerialInfo' has incomplete type

Problem in that the official Qt5.1 package for Android is compiled with Android API Level v9 where the headers "linux/serial.h" aren't included. These headers are included only beginning from Android API Level v10 and above. These headers are responsible for feature support for the custom baud rate installation.

Suggestion: Remove the "custom baud rate" support for Android, for compatibility on all Android versions.