printk: Use the BITS_PER_LONG macro

sizeof(unsigned long) * 8 is the number of bits in an unsigned long
variable, replace it with BITS_PER_LONG macro to make it simpler.
Signed-off-by: Jinjie Ruan <ruanjinjie@huawei.com>
Reviewed-by: John Ogness <john.ogness@linutronix.de>
Reviewed-by: Petr Mladek <pmladek@suse.com>
Link: https://lore.kernel.org/r/20240903035358.308482-1-ruanjinjie@huawei.comSigned-off-by: Petr Mladek <pmladek@suse.com>

kernel/printk/printk_ringbuffer.h

@@ -4,6 +4,7 @@
 #define _KERNEL_PRINTK_RINGBUFFER_H
 
 #include <linux/atomic.h>
+#include <linux/bits.h>
 #include <linux/dev_printk.h>
 #include <linux/stddef.h>
 #include <linux/types.h>
@@ -122,7 +123,7 @@ enum desc_state {
 
 #define _DATA_SIZE(sz_bits)	(1UL << (sz_bits))
 #define _DESCS_COUNT(ct_bits)	(1U << (ct_bits))
-#define DESC_SV_BITS		(sizeof(unsigned long) * 8)
+#define DESC_SV_BITS		BITS_PER_LONG
 #define DESC_FLAGS_SHIFT	(DESC_SV_BITS - 2)
 #define DESC_FLAGS_MASK		(3UL << DESC_FLAGS_SHIFT)
 #define DESC_STATE(sv)		(3UL & (sv >> DESC_FLAGS_SHIFT))