exec: Fix min/max typo in stack space calculation

exec: Fix min/max typo in stack space calculation

When handling the argc == 0 case, the stack space calculation should be
using max() not min().

Link: https://lkml.kernel.org/r/20220201190700.3147041-1-keescook@chromium.org
Signed-off-by: Kees Cook <keescook@chromium.org>
Cc: Michael Kerrisk <mtk.manpages@gmail.com>
Cc: Ariadne Conill <ariadne@dereferenced.org>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Christian Brauner <brauner@kernel.org>
Cc: Rich Felker <dalias@libc.org>
Cc: Eric Biederman <ebiederm@xmission.com>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: Shuah Khan <shuah@kernel.org>
Cc: Yang Yingliang <yangyingliang@huawei.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Stephen Rothwell <sfr@canb.auug.org.au>