Update to 5.15-rc2
- eliminated 2 patches
- patches.suse/memblock-introduce-saner-memblock_free_ptr-interface.patch
- patches.suse/tools-bootconfig-define-memblock_free_ptr-to-fix-build-error.patch
- update configs
- ARCH_NR_GPIO (1024 on x86_64, 512 on i386)
- drop WARN_DYNAMIC_STACK on s390x