Staging: sm750fb: fix hw_imageblit parameters

Fix up hw_imageblit() so that the function paramaters match up with what
the driver expects them to be when using it as a function pointer.

Cc: Sudip Mukherjee <sudipm.mukherjee@gmail.com>
Cc: Teddy Wang <teddy.wang@siliconmotion.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>