realtek: backport gpio-realtek-otto driver from 5.13 to 5.10

realtek: backport gpio-realtek-otto driver from 5.13 to 5.10

This patch backports "gpio-realtek-otto" driver to Kernel 5.10.
"MACH_REALTEK_RTL" is used as a platform name in upstream, but "RTL838X"
is used in OpenWrt, so update the dependency by the additional patch.

Note: GPIO mapping is changed in the upstreamed driver.

  old - new

   24 -  0
   25 -  1
   26 -  2
   27 -  3
   28 -  4
   29 -  5
   30 -  6
   31 -  7
   16 -  8
   17 -  9
   18 - 10
   19 - 11
   20 - 12
   21 - 13
   22 - 14
   23 - 15
    8 - 16
    9 - 17
   10 - 18
   11 - 19
   12 - 20
   13 - 21
   14 - 22
   15 - 23

Signed-off-by: INAGAKI Hiroshi <musashino.open@gmail.com>