kmemleak: use seq_hex_dump() to dump buffers

kmemleak: use seq_hex_dump() to dump buffers

Instead of custom approach let's use recently introduced seq_hex_dump()
helper.

Signed-off-by: Andy Shevchenko <[email protected]>
Cc: Alexander Viro <[email protected]>
Cc: Joe Perches <[email protected]>
Cc: Tadeusz Struk <[email protected]>
Cc: Helge Deller <[email protected]>
Cc: Ingo Tuchscherer <[email protected]>
Acked-by: Catalin Marinas <[email protected]>
Cc: Vladimir Kondratiev <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>