Allow blacklisting input devices by build flag

Usage:
TW_INPUT_BLACKLIST := accelerometer
TW_INPUT_BLACKLIST := "accelerometer\x0agyroscope"

This can be used to fix touch input on devices where an input
device is breaking touch processing in TWRP.

We are using new line chars to separate multiple devices and in
the make file you specify the new line character with \x0a which
is the hex code in ASCII for a new line.

The new line character might be a bit of a pain to use as a
delimeter, but it is highly unlikely that an OEM will ever name
an input device with a new line character in the name.

Change-Id: I255136b7a686909a23e649918c661843153c2853