i386: split cpu accelerators from cpu.c, using AccelCPUClass

i386 is the first user of AccelCPUClass, allowing to split
cpu.c into:

cpu.c            cpuid and common x86 cpu functionality
host-cpu.c       host x86 cpu functions and "host" cpu type
kvm/kvm-cpu.c    KVM x86 AccelCPUClass
hvf/hvf-cpu.c    HVF x86 AccelCPUClass
tcg/tcg-cpu.c    TCG x86 AccelCPUClass

Signed-off-by: Claudio Fontana <cfontana@suse.de>
Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>

[claudio]:
Rebased on commit b8184135 ("target/i386: allow modifying TCG phys-addr-bits")

Signed-off-by: Claudio Fontana <cfontana@suse.de>
Message-Id: <20210322132800.7470-5-cfontana@suse.de>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
diff --git a/MAINTAINERS b/MAINTAINERS
index b692c8f..c2723b3 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -351,7 +351,7 @@
 M: Richard Henderson <richard.henderson@linaro.org>
 M: Eduardo Habkost <ehabkost@redhat.com>
 S: Maintained
-F: target/i386/
+F: target/i386/tcg/
 F: tests/tcg/i386/
 F: tests/tcg/x86_64/
 F: hw/i386/