CFI: review print of Voltage values

CFI: review print of Voltage values

JEDEC standard reports Vpp integer part encoded as 4 bit HEX value.
To print it using decimal digits, %u is required.
Other voltage values are coded as BCD, so %x is appropriate.

Code already prints one nibble at a time, so no need for field width
and precision in format string.

Signed-off-by: Antonio Borneo <borneo.antonio@gmail.com>
Signed-off-by: Øyvind Harboe <oyvind.harboe@zylin.com>