parisc: stop using asm-generic/iomap.h
parisc uses custom iomap helpers to map bus specific function calls into
a linear __iomem token, but it tries to use the declarations from the x86
"generic iomap" code.
Untangle the two by duplicating the required declations and dropping
the #include that pulls in more stuff that is not needed here, to
allow simplify the generic version later.
Signed-off-by: Arnd Bergmann <arnd@arndb.de>