KVM: selftests: Move KVM_FEP macro into common library header

Move the KVM_FEP definition, a.k.a. the KVM force emulation prefix, into
processor.h so that it can be used for other tests besides the MSR filter
test.

Tested-by: Dapeng Mi <dapeng1.mi@linux.intel.com>
Link: https://lore.kernel.org/r/20240109230250.424295-26-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>

tools/testing/selftests/kvm/include/x86_64/processor.h

@@ -23,6 +23,9 @@
 extern bool host_cpu_is_intel;
 extern bool host_cpu_is_amd;
 
+/* Forced emulation prefix, used to invoke the emulator unconditionally. */
+#define KVM_FEP "ud2; .byte 'k', 'v', 'm';"
+
 #define NMI_VECTOR		0x02
 
 #define X86_EFLAGS_FIXED	 (1u << 1)

tools/testing/selftests/kvm/x86_64/userspace_msr_exit_test.c

@@ -12,8 +12,6 @@
 #include "kvm_util.h"
 #include "vmx.h"
 
-/* Forced emulation prefix, used to invoke the emulator unconditionally. */
-#define KVM_FEP "ud2; .byte 'k', 'v', 'm';"
 static bool fep_available;
 
 #define MSR_NON_EXISTENT 0x474f4f00