env: clean cmd_nvedit.c checkpatch and code style

Cleanup the cmd_nvedit.c checkpatch warnings, errors and coding style.
There are 10 wanrings left about the simple_strtoul() function:
 WARNING: simple_strtoul is obsolete, use kstrtoul instead
 #359: FILE: cmd_nvedit.c:359:
 +		load_addr = simple_strtoul(argv[2], NULL, 16);

 ...

 total: 0 errors, 10 warnings, 1043 lines checked

Signed-off-by: Igor Grinberg <grinberg@compulab.co.il>