NAND: Remove ONFI detection message to from bootup log

Without this patch, boot shows this messages upon NAND detection:

NAND:  ONFI flash detected
ONFI param page 0 valid
ONFI flash detected
ONFI param page 0 valid
128 MiB

With this patch, its back to the U-Boot "standard":

NAND:  128 MiB

Tested on x600 (SPEAr600).

Signed-off-by: Stefan Roese <sr@denx.de>
Cc: Amit Virdi <amit.virdi@st.com>
Cc: Vipin Kumar <vipin.kumar@st.com>
Cc: Scott Wood <scottwood@freescale.com>
Acked-by: Amit Virdi <amit.virdi@st.com>
Signed-off-by: Scott Wood <scott@tyr.buserror.net>