x86/apic: Silence -Wtype-limits compiler warnings

There are many compiler warnings like this,

In file included from ./arch/x86/include/asm/smp.h:13,
                 from ./arch/x86/include/asm/mmzone_64.h:11,
                 from ./arch/x86/include/asm/mmzone.h:5,
                 from ./include/linux/mmzone.h:969,
                 from ./include/linux/gfp.h:6,
                 from ./include/linux/mm.h:10,
                 from arch/x86/kernel/apic/io_apic.c:34:
arch/x86/kernel/apic/io_apic.c: In function 'check_timer':
./arch/x86/include/asm/apic.h:37:11: warning: comparison of unsigned
expression >= 0 is always true [-Wtype-limits]
   if ((v) <= apic_verbosity) \
           ^~
arch/x86/kernel/apic/io_apic.c:2160:2: note: in expansion of macro
'apic_printk'
  apic_printk(APIC_QUIET, KERN_INFO "..TIMER: vector=0x%02X "
  ^~~~~~~~~~~
./arch/x86/include/asm/apic.h:37:11: warning: comparison of unsigned
expression >= 0 is always true [-Wtype-limits]
   if ((v) <= apic_verbosity) \
           ^~
arch/x86/kernel/apic/io_apic.c:2207:4: note: in expansion of macro
'apic_printk'
    apic_printk(APIC_QUIET, KERN_ERR "..MP-BIOS bug: "
    ^~~~~~~~~~~

APIC_QUIET is 0, so silence them by making apic_verbosity type int.

Signed-off-by: Qian Cai <cai@lca.pw>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lkml.kernel.org/r/1562621805-24789-1-git-send-email-cai@lca.pw

arch/x86/include/asm/apic.h

@@ -49,7 +49,7 @@ static inline void generic_apic_probe(void)
 
 #ifdef CONFIG_X86_LOCAL_APIC
 
-extern unsigned int apic_verbosity;
+extern int apic_verbosity;
 extern int local_apic_timer_c2_ok;
 
 extern int disable_apic;

arch/x86/kernel/apic/apic.c

@@ -183,7 +183,7 @@ EXPORT_SYMBOL_GPL(local_apic_timer_c2_ok);
 /*
  * Debug level, exported for io_apic.c
  */
-unsigned int apic_verbosity;
+int apic_verbosity;
 
 int pic_mode;