Revert "runqemu: Add workaround for APIC hang on pre 4.15 kernels on qemux86"

Revert "runqemu: Add workaround for APIC hang on pre 4.15 kernels on qemux86"

This reverts commit 82e67b82ea8e12aa0b7b9db1d84fec0436dec71b.

It was commited as part of https://bugzilla.yoctoproject.org/show_bug.cgi?id=12301
for kernels < 4.15, as of now oldest builder kernel we have is 4.15 on
ubuntu 18.04 so we should not require this workaround. Moreover, this
fixes an smp problem with qemux86 where no matter what -smp <x> option
is used, qemu always starts with single core.

Signed-off-by: Khem Raj <raj.khem@gmail.com>
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>