x86-32: Disable 3D-Now in generic config

x86-32: Disable 3D-Now in generic config

We want the 686 flavour to run on Geode LX and similar AMD family 5
CPUs as well as family 6 and higher CPUs.  This used to work with
CONFIG_M686=y.  However commit 25d76ac88821 "x86/Kconfig: Explicitly
enumerate i686-class CPUs in Kconfig" in Linux 4.16 has made the
kernel require family 6 or higher.

It looks like a sensible choice would be to enable CONFIG_MGEODE_LX
and CONFIG_X86_GENERIC (for more generic optimisations), but this
currently enables CONFIG_X86_USE_3D_NOW which will cause the kernel to
crash on CPUs without the AMD-specific 3D-Now instructions.

Make CONFIG_X86_USE_3DNOW depend on CONFIG_X86_GENERIC being disabled.

Gbp-Pq: Topic bugfix/x86
Gbp-Pq: Name x86-32-disable-3dnow-in-generic-config.patch