linux-ti-mainline: Bump kernel version to v5.15
linux-ti-mainline: Bump kernel version to v5.15

This adds up numerous fixes for various k3 platforms.

While at it, bump the ti-upstream-tools repo as this sync up gives us:
config: audio_display: Update cdns-mhdp configs

Signed-off-by: Ryan Eatmon <c832a3efa8dfb59911a35349a6eeba0397feadf1@ti.com>
Signed-off-by: Nishanth Menon <50c3c575ce2bb12c45e20736ce59e86fe81915b4@ti.com>
Signed-off-by: Yogesh Siraswar <e4c3dc570d04bd480366ad8aa87a4b23b1e4ce6e@ti.com>
Signed-off-by: Denys Dmytriyenko <d29de71aea38aad3a87d486929cb0aad173ae612@konsulko.com>
Signed-off-by: Ryan Eatmon <c832a3efa8dfb59911a35349a6eeba0397feadf1@ti.com>

rcn-ee/meta-ti,rcn-ee/meta-ti,rcn-ee/meta-ti,rcn-ee/meta-ti