libdirect: Fix type cast in ARM's atomic code.
libdirect: Fix type cast in ARM's atomic code.

This is similar to commit b0db6ef94e506a74817ad34e61abf398127f111b
(libdirect: Fix type cast in MIPS' atomic code.)

lancebaiyouview/DirectFB,kaostao/directfb,mtsekm/test,jcdubois/DirectFB,lancebaiyouview/DirectFB,sklnet/DirectFB,DirectFB/directfb,dfbdok/DirectFB1,lancebaiyouview/DirectFB,lancebaiyouview/DirectFB,kevleyski/directfb,DirectFB/directfb,kevleyski/DirectFB-1,kevleyski/DirectFB-1,sklnet/DirectFB,deniskropp/DirectFB,sklnet/DirectFB,kevleyski/directfb,kaostao/directfb,djbclark/directfb-core-DirectFB,kaostao/directfb,dfbdok/DirectFB1,deniskropp/DirectFB,DirectFB/directfb,jcdubois/DirectFB,deniskropp/DirectFB,Distrotech/DirectFB,dfbdok/DirectFB1,Distrotech/DirectFB,kevleyski/directfb,djbclark/directfb-core-DirectFB,djbclark/directfb-core-DirectFB,mtsekm/test,kevleyski/DirectFB-1,mtsekm/test,jcdubois/DirectFB,djbclark/directfb-core-DirectFB,Distrotech/DirectFB,sklnet/DirectFB,kevleyski/directfb,kevleyski/DirectFB-1,deniskropp/DirectFB