mtd-utils: Fix format specifier definitions for off_t and loff_t.

mtd-utils: Fix format specifier definitions for off_t and loff_t.

On 32bit systems (e.g. ARM) the size of off_t can be 4 byte and the size of loff_t 8 byte.

This causes compiler warnings like the following:

flash_erase.c: In function 'show_progress':
flash_erase.c:56:22: warning: format '%llx' expects argument of type 'long long unsigned int', but argument 3 has type 'off_t {aka long int}' [-Wformat=]
  bareverbose(!quiet, "\rErasing %d Kibyte @ %"PRIxoff_t" -- %2i %% complete ",

and an output like this:

~# flash_erase /dev/mtd2 0 1
Erasing 64 Kibyte @ 6400000000 -- 0 % complete

~#

Since the size of off_t and loff_t can differ from each other, the
printf format specifier should be determined separately for both.
Further the format specifiers should be based directly on the size of the
particular data type.

Signed-off-by: Torsten Fleischer <torfl6749@gmail.com>
Signed-off-by: David Oberhollenzer <david.oberhollenzer@sigma-star.at>