staging: fbtft: core: set smem_len before fb_deferred_io_init call

In the Linux kernel, the following vulnerability has been resolved: staging: fbtft: core: set smem_len before fb_deferred_io_init call The fbtft_framebuffer_alloc() calls fb_deferred_io_init() before initializing info->fix.smem_len. It is set to zero by the framebuffer_alloc() function. It will trigger a WARN_ON() at the start of fb_deferred_io_init() and the function will not do anything.