selftests/powerpc/eeh: disable kselftest timeout setting for eeh-basic

The eeh-basic test got its own 60 seconds timeout (defined in commit
414f5043 "selftests/eeh: Bump EEH wait time to 60s") per breakable
device.

And we have discovered that the number of breakable devices varies
on different hardware. The device recovery time ranges from 0 to 35
seconds. In our test pool it will take about 30 seconds to run on a
Power8 system that with 5 breakable devices, 60 seconds to run on a
Power9 system that with 4 breakable devices.

Extend the timeout setting in the kselftest framework to 5 minutes
to give it a chance to finish.

Signed-off-by: Po-Hsu Lin <po-hsu.lin@canonical.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20201023024539.9512-1-po-hsu.lin@canonical.com