We don't need pde_get()'s return value, so make pde_get() return nothing

Link: https://lkml.kernel.org/r/20201211061944.GA2387571@rlkSigned-off-by: Hui Su <sh_def@163.com>
Cc: Alexey Dobriyan <adobriyan@gmail.com>
Cc: Eric W. Biederman <ebiederm@xmission.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>