nand_wait_ready is called with a millisecond delay
but the timeout used a micro second. Fixing the conversion
in the timeout call.
The prototype of the function is also changed to use an unsigned int
parameter.

Change-Id: Ia3281be7980477dfbfdb842308d35ecd8b926fb8
Signed-off-by: Lionel Debieve <lionel.debieve@st.com>
Signed-off-by: Yann Gautier <yann.gautier@st.com>