tests: Allow tc_util to use printf when requested

printk() is too simplistic and does not handle byte precision on formats
like %02x etc... printf does, so letting the possibility to use it when
relevant. This might be useful when dumping out some network packets,
byte by byte where a precision of 1 byte (thus 2 0's) is necessary.

It's better to have this output:
	41 d8 ...
instead of:
	00000041 000000d8 ...

Change-Id: Idc15bbae67830f41388373e2ca1947bb274fb550
Signed-off-by: Tomasz Bursztyka <tomasz.bursztyka@linux.intel.com>