cyclic: Rise default CYCLIC_MAX_CPU_TIME_US to 5000

The default value CYCLIC_MAX_CPU_TIME_US was 1000, which is
a little bit too low for slower hardware and sandbox.

On my MIPS Boston FPGA board with interaptiv CPU, wdt_cyclic
can easily take 3200 us to run.

On azure pipeline sandbox_clang, wdt_cyclic some times goes
beyond 1300 us.

Raise default value to 5000, which is the value already taken
by octeon_nic32. This is still sufficent to maintain system
responsiveness.

Signed-off-by: Jiaxun Yang <jiaxun.yang@flygoat.com>
Signed-off-by: Stefan Roese <sr@denx.de>