tests: newlib: disable bluetooth for now

When trying to build with newlib we get:

hci_driver.c: In function 'hci_driver_open':
hci_driver.c:389:10:
error: format '%d' expects argument of type 'int', but argument 2 has
type 'uint32_t {aka long unsigned int}' [-Werror=format=]
   BT_ERR("Required RAM size: %d, supplied: %u.", err,
          ^

This is because we have different types for {u}int32_t between newlib
and mini-libc.  We have to decide how we are going to handle this going
forward.  Various options include use of PRIu32, making mini-libc match
newlib's types, disabling the -Werror=format, etc.

Change-Id: I5df8fa05dd7658e1f6b2eeb8fa84e3270f3dd208
Signed-off-by: Kumar Gala <kumar.gala@linaro.org>