mhi: core: expand mhi_buf structure to describe additional bufferptr types

/**

 * struct mhi_buf - Describes the buffer

 * @page: buffer as a page

 * @buf: cpu address for the buffer

 * @phys_addr: physical address of the buffer

 * @dma_addr: iommu address for the buffer

 * @skb: skb of ip packet

 * @len: # of bytes

 * @name: Buffer label, for offload channel configurations name must be:

 * ECA - Event context array data

 * CCA - Channel context array data

 */

struct mhi_buf {

	struct list_head node;

	struct page *page;

	void *buf;

	phys_addr_t phys_addr;

	dma_addr_t dma_addr;

	struct sk_buff *skb;

	size_t len;

	const char *name; /* ECA, CCA */

};