kernel: bump 5.15 to 5.15.115

Manually rebased:
	backport-5.15/603-v5.19-page_pool-Add-recycle-stats-to-page_pool_put_page_bu.patch
	pending-5.15/723-net-mt7531-ensure-all-MACs-are-powered-down-before-r.patch*

Removed upstreamed:
	generic-backport/610-v6.3-net-page_pool-use-in_softirq-instead.patch[1]
	backport-5.15/705-12-v6.0-net-dsa-mt7530-rework-mt753-01-_setup.patch[2]
	backport-5.15/790-v6.4-0010-net-dsa-mt7530-split-off-common-parts-from-mt7531_se.patch[3]
	backport-5.15/703-10-v5.16-net-dsa-introduce-helpers-for-iterating-through-port.patch[4]

All other patches automatically rebased.

* Modified to define the variable i as suggested by DragonBluep in PR discussion.
  See: https://github.com/openwrt/openwrt/pull/12823#issuecomment-1578518576

1. https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?h=v5.15.115&id=3af319d5147454dc63665ef451229c674b538377
2. https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?h=v5.15.115&id=0753c1ef24194580f7165ae6e259b59a851392f2
3. https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?h=v5.15.115&id=5a7266feaa6d708fc6880a161786eaa884ef3c8e
4. 9902f91cf6

Build system: x86_64
Build-tested: bcm2711/RPi4B, ramips/tplink_archer-a6-v3, filogic/xiaomi_redmi-router-ax6000-ubootmod
Run-tested: bcm2711/RPi4B, ramips/tplink_archer-a6-v3, filogic/xiaomi_redmi-router-ax6000-ubootmod

Signed-off-by: John Audia <therealgraysky@proton.me>
(cherry picked from commit 5714660643)

target/linux/generic/pending-5.15/723-net-mt7531-ensure-all-MACs-are-powered-down-before-r.patch

@@ -10,12 +10,21 @@ The datasheet [1] explicit describes it as requirement for a reset.
 
 Signed-off-by: Alexander Couzens <lynxis@fe80.eu>
 ---
- drivers/net/dsa/mt7530.c | 4 ++++
- 1 file changed, 4 insertions(+)
+ drivers/net/dsa/mt7530.c | 6 +++++-
+ 1 file changed, 5 insertions(+), 1 deletion(-)
 
 --- a/drivers/net/dsa/mt7530.c
 +++ b/drivers/net/dsa/mt7530.c
-@@ -2440,6 +2440,10 @@ mt7531_setup(struct dsa_switch *ds)
+@@ -2412,7 +2412,7 @@ mt7531_setup(struct dsa_switch *ds)
+ 	struct mt7530_priv *priv = ds->priv;
+ 	struct mt7530_dummy_poll p;
+ 	u32 val, id;
+-	int ret;
++	int ret, i;
+ 
+ 	/* Reset whole chip through gpio pin or memory-mapped registers for
+ 	 * different type of hardware
+@@ -2444,6 +2444,10 @@ mt7531_setup(struct dsa_switch *ds)
  		return -ENODEV;
  	}