package/frr: bump to version 8.1

- host-elfutils is mandatory since version 8.0 and
  https://github.com/FRRouting/frr/commit/5609b3af497c44d980aad2bc7d6332dedd7974e7
- This bump is needed to fix the following build failure since bump of
  libyang to version 2.0.112 in commit
  2a3edc5e00b38f4f927894d0911990c9060e4415:

In file included from lib/northbound.c:20:
lib/northbound.c: In function 'nb_node_check_config_only':
lib/northbound.c:97:22: error: dereferencing pointer to incomplete type 'const struct lys_node'
   97 |  if (CHECK_FLAG(snode->flags, LYS_CONFIG_R)) {
      |                      ^~

- Update indentation in hash file (two spaces)

https://github.com/FRRouting/frr/releases/tag/frr-8.0
https://github.com/FRRouting/frr/releases/tag/frr-8.1

Fixes:
 - http://autobuild.buildroot.org/results/bd779ee960ba2181bc60313569c77c1e60b4e726

Signed-off-by: Fabrice Fontaine <fontaine.fabrice@gmail.com>
Signed-off-by: Arnout Vandecappelle (Essensium/Mind) <arnout@mind.be>

package/frr/frr.hash

@@ -1,3 +1,3 @@
 # Locally calculated
-sha256 030d4e66f577726dfea13bd3a9c669fd41d8fd89b25953a36b5b0966d406ff28  frr-7.5.1.tar.gz
-sha256 8177f97513213526df2cf6184d8ff986c675afb514d4e68a404010521b880643  COPYING
+sha256  9d82c11b304ab89a30627fcbb4150f51e639f473f8563976e14101e796240599  frr-8.1.tar.gz
+sha256  8177f97513213526df2cf6184d8ff986c675afb514d4e68a404010521b880643  COPYING

package/frr/frr.mk

@@ -4,7 +4,7 @@
 #
 ################################################################################
 
-FRR_VERSION = 7.5.1
+FRR_VERSION = 8.1
 FRR_SITE = $(call github,FRRouting,frr,frr-$(FRR_VERSION))
 FRR_LICENSE = GPL-2.0
 FRR_LICENSE_FILES = COPYING
@@ -15,7 +15,7 @@ FRR_AUTORECONF = YES
 FRR_DEPENDENCIES = host-frr readline json-c \
 	libyang libnl c-ares
 
-HOST_FRR_DEPENDENCIES = host-flex host-bison host-python3
+HOST_FRR_DEPENDENCIES = host-flex host-bison host-elfutils host-python3
 
 FRR_CONF_OPTS = --with-clippy=$(HOST_DIR)/bin/clippy \
 	--sysconfdir=/etc/frr \