staging: sm750fb: sm750_accel: Provide description for 'accel' and fix function naming

staging: sm750fb: sm750_accel: Provide description for 'accel' and fix function naming

Fixes the following W=1 kernel build warning(s):

 drivers/staging/sm750fb/sm750_accel.c:155: warning: Function parameter or member 'accel' not described in 'sm750_hw_copyarea'
 drivers/staging/sm750fb/sm750_accel.c:155: warning: expecting prototype for sm750_hm_copyarea(). Prototype was for sm750_hw_copyarea() instead
 drivers/staging/sm750fb/sm750_accel.c:321: warning: Function parameter or member 'accel' not described in 'sm750_hw_imageblit'

Cc: Sudip Mukherjee <sudipm.mukherjee@gmail.com>
Cc: Teddy Wang <teddy.wang@siliconmotion.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: linux-fbdev@vger.kernel.org
Cc: linux-staging@lists.linux.dev
Signed-off-by: Lee Jones <lee.jones@linaro.org>
Link: https://lore.kernel.org/r/20210414181129.1628598-26-lee.jones@linaro.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>