x86/vmx: Skip vmx_pf_exception_test_fep early if FEP is not available

The check to skip the test is currently performed in the guest code.
There a few TEST_ASSERTs that happen before the guest is run, which
internally call report_passed(). The latter increases the number of
passed tests.

Hence, when vmx_pf_exception_test_fep is run, report_summary() does not
return a "skip" error code because the total number of tests is larger
than the number of skipped tests.

Skip early if FEP is not available, before any assertions, such that
report_summary() finds exactly 1 skipped test and returns the
appropriate error code.

Signed-off-by: Yosry Ahmed <yosry.ahmed@linux.dev>
Link: https://patch.msgid.link/20251110232642.633672-3-yosry.ahmed@linux.dev
[sean: use early return instead of if-else]
Signed-off-by: Sean Christopherson <seanjc@google.com>

Author: yosrym93

x86/vmx_tests.c

@@ -10644,6 +10644,11 @@ static void vmx_pf_exception_test(void)
 
 static void vmx_pf_exception_forced_emulation_test(void)
 {
+	if (!is_fep_available) {
+		report_skip("Forced emulation prefix (FEP) not available\n");
+		return;
+	}
+
 	__vmx_pf_exception_test(NULL, NULL, vmx_pf_exception_forced_emulation_test_guest);
 }