generic: 5.15: backport PPC VDSO executable stack fix

generic: 5.15: backport PPC VDSO executable stack fix

Recent binutils will warn if there is no .note.GNU-stack section and will
interpret that as that stack is executable.

So, lets modify the upstream 6.1 fix as in 5.15 VDSO32 and VDSO64 are still
separate but later they were merged to resolve:
/external-toolchain/openwrt-toolchain-mpc85xx-p1020_gcc-12.3.0_musl.Linux-x86_64/toolchain-powerpc_8548_gcc-12.3.0_musl/bin/../lib/gcc/powerpc-openwrt-linux-musl/12.3.0/../../../../powerpc-openwrt-linux-musl/bin/ld: warning: arch/powerpc/kernel/vdso32/getcpu.o: missing .note.GNU-stack section implies executable stack
/external-toolchain/openwrt-toolchain-mpc85xx-p1020_gcc-12.3.0_musl.Linux-x86_64/toolchain-powerpc_8548_gcc-12.3.0_musl/bin/../lib/gcc/powerpc-openwrt-linux-musl/12.3.0/../../../../powerpc-openwrt-linux-musl/bin/ld: NOTE: This behaviour is deprecated and will be removed in a future version of the linker

Signed-off-by: Robert Marko <robimarko@gmail.com>