phy.c: make less verbose - turn printf() into debug()

The PHY driver was too verbose and corrupted the boot message display
like this:

	...
	Net:   TSEC0 connected to Marvell 88E1111S
	TSEC1 connected to Marvell 88E1111S
	TSEC0, TSEC1
	...

Turn printf() into debug() so we het the expected output again:

	...
	Net:   TSEC0, TSEC1
	...

Signed-off-by: Wolfgang Denk <wd@denx.de>
Cc: Kumar Gala <galak@kernel.crashing.org>