perf build: Fix a build error on 32-bit x86

The commit d7507a94a0 ("KVM: SVM: Treat exit_code as an unsigned
64-bit value through all of KVM") added "ull" suffix to SVM exit codes
and it makes the 32-bit build fail like below.

  In file included from util/kvm-stat-arch/kvm-stat-x86.c:4:
  util/kvm-stat-arch/../../../arch/x86/include/uapi/asm/svm.h:137:32:
             error: conversion from 'long long unsigned int' to 'long unsigned int' changes
                    value from '18446744073709551615' to '4294967295' [-Werror=overflow]
    137 | #define SVM_EXIT_ERR           -1ull
        |                                ^
  util/kvm-stat-arch/../kvm-stat.h:131:17: note: in definition of macro 'define_exit_reasons_table'
    131 |                 symbols, { -1, NULL }                   \
        |                 ^~~~~~~
  util/kvm-stat-arch/../../../arch/x86/include/uapi/asm/svm.h:249:11: note: in expansion of macro 'SVM_EXIT_ERR'
    249 |         { SVM_EXIT_ERR,         "invalid_guest_state" }
        |           ^~~~~~~~~~~~
  util/kvm-stat-arch/kvm-stat-x86.c:12:45: note: in expansion of macro 'SVM_EXIT_REASONS'
     12 | define_exit_reasons_table(svm_exit_reasons, SVM_EXIT_REASONS);
        |                                             ^~~~~~~~~~~~~~~~

As the exit_code was unsigned long, the compiler complained about the
truncation.  Let's convert it to u64 to suppress the error.

Fixes: fac520e43a ("tools headers: Sync KVM headers with the kernel sources")
Signed-off-by: Namhyung Kim <namhyung@kernel.org>

tools/perf/util/kvm-stat.h

@@ -69,7 +69,7 @@ struct kvm_events_ops {
 };
 
 struct exit_reasons_table {
-	unsigned long exit_code;
+	u64 exit_code;
 	const char *reason;
 };