xtensa: drop ARCH_WANT_FRAME_POINTERS

ARCH_WANT_FRAME_POINTERS was enabled in the xtensa Kconfig in the commit
8f371c75 ("xtensa: enable lockdep support"), but neither windowed
nor call0 xtensa ABI need frame pointers for stack tracing.
Drop ARCH_WANT_FRAME_POINTERS from the xtensa Kconfig.
Drop ftrace_return_address0 definition as the generic implementation is
correct.

Signed-off-by: Max Filippov <jcmvbkbc@gmail.com>