kdump: use print_mask_arg0 appropriately

[kevans]

Summary

Some callers are using print_mask_arg() when they should be using
print_mask_arg0(); the latter should be used when all flags are optional
and there's not a flag to be decoded with a 0-mask.  This turns:

nmount(0x6991e009000,0x8,0<><invalid>0)

into:

nmount(0x6991e009000,0x8,0)

[kevans]

Whoops, fix inconsistent blank line

[jhb]

usr.bin/kdump/kdump.c

248

This exists for those cases. Probably nmount() needs to use print_mask_arg0 instead? Some flags require at least one flag to be set, and that is why print_mask_arg has this behavior.

[kevans]

Use the correct print_mask_arg* variant; at least close_range(2) and all of the
*mount() syscalls are flag-optional and no 0-mask flag to be decoded.

[jhb]

Pointy hat to me for the *mount() ones.