disk: gpt: print all partitions

disk: gpt: print all partitions

For GPT partition tables the 'part list' command stops at the first invalid
partition number. But Ubuntu has images with partitions number

    1, 12, 13, 14, 15

In this case only partition 1 was listed by 'part list'.

Fixes: 38a3021edc54 ("disk: part_efi: remove indent level from loop")
Reported-by: Alexandre Ghiti <alexandre.ghiti@canonical.com>
Signed-off-by: Heinrich Schuchardt <heinrich.schuchardt@canonical.com>
Tested-by: Alexandre Ghiti <alexandre.ghiti@canonical.com>