uclibc: disable parallel build for uClibc 0.9.31

This is only required for uClibc 0.9.31 and this veriosn is only used by
AVR32 so could be safely removed together with AVR32.

Even 0.9.32 builds well in parallel (at least on x86) so IMHO there's no need
in >= 0.9.33, just disable for a particular broken version.

Signed-off-by: Alexey Brodkin <abrodkin@synopsys.com>

Cc: Anton Kolesov <akolesov@synopsys.com>
Cc: Peter Korsgaard <peter@korsgaard.com>
Cc: Gustavo Zacarias <gustavo@zacarias.com.ar>
Cc: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Cc: Thomas De Schampheleire <patrickdepinguin@gmail.com>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>