render/vulkan: Fix draw rect clip region invalid in blend none mode
wlr_render_pass_add_rect() set clip in vulkan renderer donot working.
render_pass_add_rect in WLR_RENDER_BLEND_MODE_NONE case use vkCmdClearAttachments() not vkCmdDraw(), vkCmdSetScissor() not effect ClearAttachment() rect only use VkClearRect param
Edited by YongXing