[PARISC] Add dummy isa_(bus|virt)_to_(virt|bus) inlines

Less painful than fixing up the Kconfig for a pile of drivers to only build
on X86 && ARM && MIPS...

Just make them BUG(), as defining them to be 1:1 with physical memory will
likely HPMC the box anyways.

Signed-off-by: Kyle McMartin <[e-mail]>

include/asm-parisc/io.h

···
 #define virt_to_bus virt_to_phys
 #define bus_to_virt phys_to_virt
 
+static inline unsigned long isa_bus_to_virt(unsigned long addr) {
+	BUG();
+	return 0;
+}
+
+static inline unsigned long isa_virt_to_bus(void *addr) {
+	BUG();
+	return 0;
+}
+
 /*
  * Memory mapped I/O
  *