x86: fix ioremap pgprot inconsistency

The pgprot flags which are handed into ioremap_page_range() are
different to those which are set in change_page_attr(). The
ioremap_page_range flags are executable, while the c_p_a flags are
not.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Ingo Molnar <mingo@elte.hu>