KVM: x86: Change return type of is_long_mode() to bool

Change return type of is_long_mode() to bool to avoid implicit cast,
as literally every user of is_long_mode() treats its return value as a
boolean.

Signed-off-by: Binbin Wu <binbin.wu@linux.intel.com>
Link: https://lore.kernel.org/r/20230322045824.22970-5-binbin.wu@linux.intel.com


Reviewed-by: Kai Huang <kai.huang@intel.com>
Signed-off-by: Sean Christopherson <seanjc@google.com>