x86/asm: Fix SETZ size enqcmds() build failure

When building under GCC 4.9 and 5.5:

  arch/x86/include/asm/special_insns.h: Assembler messages:
  arch/x86/include/asm/special_insns.h:286: Error: operand size mismatch for `setz'

Change the type to "bool" for condition code arguments, as documented.

Fixes: 7f5933f8 ("x86/asm: Add an enqcmds() wrapper for the ENQCMDS instruction")
Co-developed-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Borislav Petkov <bp@suse.de>
Link: https://lkml.kernel.org/r/20210910223332.3224851-1-keescook@chromium.org