realtek: board: add patch to fix boot hang

realtek: board: add patch to fix boot hang

Add a patch to fix boot hang on some devices after 7cc31af7bdd4
("realtek: convert to generic machine initialization"), reusing
upstream's implementation of Realtek board setup. The issue came up on a
Linksys LGS352C device, causing total silence and a hang after
rt-loader's last line "Booting kernel from 0x80100000 ...".

While the OpenWrt downstream version operated on the plain appended
device tree using a pointer, the upstream implementation copies the FDT
into a 16 KiB buffer. Given the following survey, this may be too small
for some devices:

  rtl9311_linksys_lgs352c:                21278 bytes
  rtl9313_ubnt_usw-pro-xg-8-poe:          12809 bytes
  rtl9313_hasivo_f5800w-12s-plus:         13103 bytes
  rtl9313_xikestor_sks8300-12x-v1:        13630 bytes
  rtl9313_zyxel_xs1930-12f:               14488 bytes
  rtl9313_zyxel_xs1930-12hp:              15234 bytes
  rtl9313_hasivo_s1300wp-8xgt-4s-plus:    15341 bytes

To fix this, the patch increases the buffer size, leaving some more
headroom for further outliers.

Fixes: 7cc31af7bdd4 ("realtek: convert to generic machine initialization")
Assisted-by: Claude:claude-sonnet-5
Link: https://github.com/openwrt/openwrt/pull/24541
Signed-off-by: Jonas Jelonek <jelonek.jonas@gmail.com>