selftests/powerpc: Run fpu_preempt test for 60 seconds

The FPU preempt test only runs for 20 seconds, which is not particularly
long. Run it for 60 seconds to increase the chance of detecting
corruption.

Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://msgid.link/20231128132748.1990179-4-mpe@ellerman.id.au

tools/testing/selftests/powerpc/math/fpu_preempt.c

@@ -22,7 +22,7 @@
 #include "fpu.h"
 
 /* Time to wait for workers to get preempted (seconds) */
-#define PREEMPT_TIME 20
+#define PREEMPT_TIME 60
 /*
  * Factor by which to multiply number of online CPUs for total number of
  * worker threads