zink: Don't set dynamic color attachment state for 0 attachments.

zink: Don't set dynamic color attachment state for 0 attachments.

Fixes some validation failures like:

VUID-vkCmdSetColorBlendEquationEXT-attachmentCount-arraylength(ERROR / SPEC): msgNum: -175001922 - Validation Error: [ VUID-vkCmdSetColorBlendEquationEXT-attachmentCount-arraylength ] Object 0: handle = 0xaaaae7632fa0, type = VK_OBJECT_TYPE_DEVICE; | MessageID = 0xf591aebe | vkCmdSetColorBlendEquationEXT: parameter attachmentCount must be greater than 0. The Vulkan spec states: attachmentCount must be greater than 0 (https://www.khronos.org/registry/vulkan/specs/1.3-extensions/html/vkspec.html#VUID-vkCmdSetColorBlendEquationEXT-attachmentCount-arraylength)

However, we still have some around dynamic color attachment state:

    Objects: 1
        [0] 0xaaaafcab4150, type: 6, name: NULL
VUID_Undefined(ERROR / SPEC): msgNum: 2044605652 - Validation Error: [ VUID_Undefined ] Object 0: handle = 0xaaaafcab4150, type = VK_OBJECT_TYPE_COMMAND_BUFFER; | MessageID = 0x79de34d4 | VkCommandBuffer 0xaaaafcab4150[]: Dynamic color blend enable state not set for this command buffer.
    Objects: 1
        [0] 0xaaaafcab4150, type: 6, name: NULL
VUID_Undefined(ERROR / SPEC): msgNum: 2044605652 - Validation Error: [ VUID_Undefined ] Object 0: handle = 0xaaaafcab4150, type = VK_OBJECT_TYPE_COMMAND_BUFFER; | MessageID = 0x79de34d4 | VkCommandBuffer 0xaaaafcab4150[]: Dynamic color blend equation state not set for this command buffer.
    Objects: 1
        [0] 0xaaaafcab4150, type: 6, name: NULL
VUID_Undefined(ERROR / SPEC): msgNum: 2044605652 - Validation Error: [ VUID_Undefined ] Object 0: handle = 0xaaaafcab4150, type = VK_OBJECT_TYPE_COMMAND_BUFFER; | MessageID = 0x79de34d4 | VkCommandBuffer 0xaaaafcab4150[]: Dynamic color write mask state not set for this command buffer.

Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/20186>