rtlwifi: btcoexist: re-use %*ph specifier to hexdump

Instead of printing each byte from the given buffer the code is converted to
use %*ph specifier.

Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>