The optimized find bit functions are only implemented for 32 bit and are
not built on aarch64 systems. Therefore, for example bootchooser cannot
be build for aarch64.

Select the generic find_bit implementations on aarch64.

As the decision, if lib64 or lib32 is build or not, directly depends on
CPU_V8, the generic implementation also should be used if CPU_V8 is
selected.

Reported-by: Thomas Hämmerle <Thomas.Haemmerle@wolfvision.net>
Signed-off-by: Michael Tretter <m.tretter@pengutronix.de>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>