kexec: fix the unexpected kexec_dprintk() macro

Jiri reported that the current kexec_dprintk() always prints out debugging
message whenever kexec/kdmmp loading is triggered.  That is not wanted. 
The debugging message is supposed to be printed out when 'kexec -s -d' is
specified for kexec/kdump loading.

After investigating, the reason is the current kexec_dprintk() takes
printk(KERN_INFO) or printk(KERN_DEBUG) depending on whether '-d' is
specified.  However, distros usually have defaulg log level like below:

 [~]# cat /proc/sys/kernel/printk
 7       4      1       7

So, even though '-d' is not specified, printk(KERN_DEBUG) also always
prints out.  I thought printk(KERN_DEBUG) is equal to pr_debug(), it's
not.

Fix it by changing to use pr_info() instead which are expected to work.

Link: https://lkml.kernel.org/r/[email protected]
Fixes: cbc2fe9 ("kexec_file: add kexec_file flag to control debug printing")
Signed-off-by: Baoquan He <[email protected]>
Reported-by: Jiri Slaby <[email protected]>
Closes: https://lore.kernel.org/all/[email protected]
Reviewed-by: Dave Young <[email protected]>
Cc: <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>

Author: Baoquan He

include/linux/kexec.h

@@ -461,10 +461,8 @@ static inline void arch_kexec_pre_free_pages(void *vaddr, unsigned int pages) {
 
 extern bool kexec_file_dbg_print;
 
-#define kexec_dprintk(fmt, ...)					\
-	printk("%s" fmt,					\
-	       kexec_file_dbg_print ? KERN_INFO : KERN_DEBUG,	\
-	       ##__VA_ARGS__)
+#define kexec_dprintk(fmt, arg...) \
+        do { if (kexec_file_dbg_print) pr_info(fmt, ##arg); } while (0)
 
 #else /* !CONFIG_KEXEC_CORE */
 struct pt_regs;