macintosh/via-pmu: Avoid compiler warnings when CONFIG_PROC_FS is disabled

drivers/macintosh/via-pmu.c:897:12: warning: 'pmu_battery_proc_show' defined but not used [-Wunused-function]
 static int pmu_battery_proc_show(struct seq_file *m, void *v)
            ^~~~~~~~~~~~~~~~~~~~~
drivers/macintosh/via-pmu.c:871:12: warning: 'pmu_irqstats_proc_show' defined but not used [-Wunused-function]
 static int pmu_irqstats_proc_show(struct seq_file *m, void *v)
            ^~~~~~~~~~~~~~~~~~~~~~
drivers/macintosh/via-pmu.c:860:12: warning: 'pmu_info_proc_show' defined but not used [-Wunused-function]
 static int pmu_info_proc_show(struct seq_file *m, void *v)
            ^~~~~~~~~~~~~~~~~~

Add some #ifdefs to avoid unused code warnings when CONFIG_PROC_FS is
disabled.
Reported-by: Randy Dunlap <rdunlap@infradead.org>
Suggested-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Signed-off-by: Finn Thain <fthain@linux-m68k.org>
Tested-by: Randy Dunlap <rdunlap@infradead.org>
Acked-by: Randy Dunlap <rdunlap@infradead.org>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/0c11c0770fc4ec7e80a4b2e0ffce1055b792cfdb.1647854880.git.fthain@linux-m68k.org

drivers/macintosh/via-pmu.c

@@ -203,9 +203,11 @@ static int init_pmu(void);
 static void pmu_start(void);
 static irqreturn_t via_pmu_interrupt(int irq, void *arg);
 static irqreturn_t gpio1_interrupt(int irq, void *arg);
+#ifdef CONFIG_PROC_FS
 static int pmu_info_proc_show(struct seq_file *m, void *v);
 static int pmu_irqstats_proc_show(struct seq_file *m, void *v);
 static int pmu_battery_proc_show(struct seq_file *m, void *v);
+#endif
 static void pmu_pass_intr(unsigned char *data, int len);
 static const struct proc_ops pmu_options_proc_ops;
 
@@ -852,6 +854,7 @@ query_battery_state(void)
 			2, PMU_SMART_BATTERY_STATE, pmu_cur_battery+1);
 }
 
+#ifdef CONFIG_PROC_FS
 static int pmu_info_proc_show(struct seq_file *m, void *v)
 {
 	seq_printf(m, "PMU driver version     : %d\n", PMU_DRIVER_VERSION);
@@ -972,6 +975,7 @@ static const struct proc_ops pmu_options_proc_ops = {
 	.proc_release	= single_release,
 	.proc_write	= pmu_options_proc_write,
 };
+#endif
 
 #ifdef CONFIG_ADB
 /* Send an ADB command */