[intelxl] Use one admin queue buffer per admin queue descriptor

We currently use a single data buffer shared between all admin queue
descriptors.  This works for the physical function driver since we
have at most one command in progress and only a single event (which
does not use a data buffer).

The communication path between the physical and virtual function
drivers uses the event data buffer, and there is no way to prevent a
solicited event (i.e. a response to a request) from being overwritten
by an unsolicited event (e.g. a link status change).

Provide individual data buffers for each admin event queue descriptor
(and for each admin command queue descriptor, for the sake of
consistency).

Signed-off-by: Michael Brown <mcb30@ipxe.org>

src/drivers/net/intelxl.h

@@ -319,6 +319,8 @@ union intelxl_admin_buffer {
 	struct intelxl_admin_switch_buffer sw;
 	/** Get VSI Parameters data buffer */
 	struct intelxl_admin_vsi_buffer vsi;
+	/** Alignment padding */
+	uint8_t pad[INTELXL_ALIGN];
 } __attribute__ (( packed ));
 
 /** Admin queue descriptor */
@@ -358,6 +360,8 @@ struct intelxl_admin_descriptor {
 struct intelxl_admin {
 	/** Descriptors */
 	struct intelxl_admin_descriptor *desc;
+	/** Data buffers */
+	union intelxl_admin_buffer *buf;
 	/** Queue index */
 	unsigned int index;
 
@@ -365,8 +369,6 @@ struct intelxl_admin {
 	unsigned int base;
 	/** Register offsets */
 	const struct intelxl_admin_offsets *regs;
-	/** Data buffer */
-	union intelxl_admin_buffer *buffer;
 };
 
 /**