Created separate isa_ids.h file and a utility function to print out ISA

IDs in a human-readable format.

src/drivers/bus/isa_ids.c

@@ -0,0 +1,24 @@
+#include "etherboot.h"
+#include "isa_ids.h"
+
+/* 
+ * EISA and ISAPnP IDs are actually mildly human readable, though in a
+ * somewhat brain-damaged way.
+ *
+ */
+char * isa_id_string ( uint16_t vendor, uint16_t product ) {
+	static unsigned char buf[7];
+	int i;
+
+	/* Vendor ID is a compressed ASCII string */
+	vendor = htons ( vendor );
+	for ( i = 2 ; i >= 0 ; i-- ) {
+		buf[i] = ( 'A' - 1 + ( vendor & 0x1f ) );
+		vendor >>= 5;
+	}
+	
+	/* Product ID is a 4-digit hex string */
+	sprintf ( &buf[3], "%hx", htons ( product ) );
+
+	return buf;
+}