tests: fpu_sharing: avoid stack overflow due to unnecessary feature

CONFIG_FPU selects support for formatting floating point numbers,
which increases the stack requirements for cbprintf, causing this test
to overrun its stack.

Since this test doesn't format floating point numbers, use
CBPRINTF_NANO to revert to using the small-footprint formatter.

Signed-off-by: Peter Bigot <peter.bigot@nordicsemi.no>
1 file changed