pmbootstrap kconfig edit|migrate: should need exactly 1 argument

Right now it is possible to run pmbootstrap kconfig edit and pmbootstrap will crash later on. It should stop with saying that exactly 1 argument is required.

The fix is probably something like the following, though it creates a list of kernels instead of one kernel string. So related code needs to be adjusted too. I've also tried required=True, but that didn't really make it a required argument (I guess because it is a positional argument?).

diff --git a/pmb/parse/arguments.py b/pmb/parse/arguments.py
index c1c6c15b..a6acf20f 100644
--- a/pmb/parse/arguments.py
+++ b/pmb/parse/arguments.py
@@ -683,7 +683,7 @@ def arguments_kconfig(subparser):
         action="store_true",
         help="use nconfig rather than menuconfig for kernel" " configuration",
     )
-    add_kernel_arg(edit)
+    add_kernel_arg(edit, nargs=1)
 
     # "pmbootstrap kconfig migrate"
     migrate = sub.add_parser(
@@ -696,7 +696,7 @@ def arguments_kconfig(subparser):
     migrate.add_argument(
         "--arch", choices=arch_choices, dest="arch", type=lambda x: Arch.from_str(x)
     )
-    add_kernel_arg(migrate)
+    add_kernel_arg(migrate, nargs=1)
 
 
 def arguments_repo_bootstrap(subparser):