blue: enable the UHID driver

The userspace HID driver, which is needed by the JB Bluetooth stack
to process input from Bluetooth keyboards, has been merged by commit
2a86b6381ea84610722c8e27dc5cd12e0fb4fce7 , but its configuration has
not been enabled. Thus, the driver does not get built together with
the kernel, and the functionality it provides is not available.

Change-Id: I33d552100ae7b2304818201cefc6d32120813192