x86: Clean up ioremap()

Use ioremap() as the main implemented function, and defines
ioremap_nocache() as a deprecated alias of ioremap() in
preparation of removing ioremap_nocache() entirely.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>