samples/bpf: Drop unnecessary fallthrough

__fallthrough is now not supported. Instead of renaming it to
now-canonical ([0]) fallthrough pseudo-keyword, just get rid of it and
equate 'h' case to default case, as both emit usage information and
succeed.

  [0] https://www.kernel.org/doc/html/latest/process/deprecated.html?highlight=fallthrough#implicit-switch-case-fall-through

Signed-off-by: Andrii Nakryiko <[email protected]>
Signed-off-by: Daniel Borkmann <[email protected]>
Acked-by: Yonghong Song <[email protected]>
Link: https://lore.kernel.org/bpf/[email protected]

Author: anakryiko

samples/bpf/hbm.c

@@ -498,7 +498,6 @@ int main(int argc, char **argv)
 					"Option -%c requires an argument.\n\n",
 					optopt);
 		case 'h':
-			__fallthrough;
 		default:
 			Usage();
 			return 0;