driver core: firmware_class:fix memory leak of page pointers array

The page pointers array is allocated in fw_realloc_buffer() called by
firmware_data_write(), and should be freed in release function of firmware
device.

Signed-off-by: Ming Lei <tom.leiming@gmail.com>
Reported-by: Catalin Marinas <catalin.marinas@arm.com>
Acked-by: David Woodhouse <David.Woodhouse@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>