x86, MCE, AMD: Make error_count read only

Until now, writing to error count caused the code to reset the
thresholding bank to the current thresholding limit and start counting
errors from the beginning.

This is misleading and unclear, and can be accomplished by writing the
old thresholding limit into ->threshold_limit.

Make error_count read-only with the functionality to show the current
error count.

Signed-off-by: Borislav Petkov <borislav.petkov@amd.com>

arch/x86/kernel/cpu/mcheck/mce_amd.c

@@ -369,14 +369,10 @@ static ssize_t show_error_count(struct threshold_block *b, char *buf)
 				     (THRESHOLD_MAX - b->threshold_limit)));
 }
 
-static ssize_t store_error_count(struct threshold_block *b,
-				 const char *buf, size_t count)
-{
-	struct thresh_restart tr = { .b = b, .reset = 1, .old_limit = 0 };
-
-	smp_call_function_single(b->cpu, threshold_restart_bank, &tr, 1);
-	return 1;
-}
+static struct threshold_attr error_count = {
+	.attr = {.name = __stringify(error_count), .mode = 0444 },
+	.show = show_error_count,
+};
 
 #define RW_ATTR(val)							\
 static struct threshold_attr val = {					\
@@ -387,7 +383,6 @@ static struct threshold_attr val = {					\
 
 RW_ATTR(interrupt_enable);
 RW_ATTR(threshold_limit);
-RW_ATTR(error_count);
 
 static struct attribute *default_attrs[] = {
 	&threshold_limit.attr,