[PARISC] Fix compile warning caused by conflicting types of expand_upwards()

Fix compile warning caused by conflicting types of expand_upwards. IA64
requires it to not be static inline, as it's used outside mm/mmap.c

Signed-off-by: Matthew Wilcox <willy@parisc-linux.org>
Signed-off-by: Kyle McMartin <kyle@parisc-linux.org>