debuginfod/debuginfod-client.c: use long for cache time configurations

debuginfod/debuginfod-client.c: use long for cache time configurations

time_t is platform dependent and some of architectures e.g.
x32, riscv32, arc use 64bit time_t even while they are 32bit
architectures, therefore directly using integer printf formats will not
work portably.

Use a plain long everywhere as the intervals are small enough
that it will not be problematic.

Signed-off-by: Alexander Kanavin <alex@linutronix.de>