staging: fbtft: Use devm_kcalloc instead of devm_kzalloc

staging: fbtft: Use devm_kcalloc instead of devm_kzalloc

Replace devm_kzalloc with devm_kcalloc to ensure there are no integer
overflows from the multiplication of a number * sizeof

The following Coccinelle semantic patch was used to make this change:
//<smpl>
@@
expression dev,E1,E2,E3,E4;
@@

- devm_kzalloc(dev,E1*E2*sizeof(E3),E4)
+ devm_kcalloc(dev,E1*E2,sizeof(E3),E4)
//</smpl>

Signed-off-by: Amitoj Kaur Chawla <amitoj1606@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>