microblaze: Change extern inline to static inline

microblaze: Change extern inline to static inline

With compilers which follow the C99 standard (like modern versions of gcc and
clang), "extern inline" does the opposite thing from older versions of gcc
(emits code for an externally linkable version of the inline function).

"static inline" does the intended behavior in all cases instead.

Description taken from:
"staging, rtl8192e, LLVMLinux: Change extern inline to static inline"
(sha1: 890a6007ff687d3906b029cde68747209f81d264)

The patch removes compilation warnings W=1:
./arch/microblaze/include/asm/delay.h:18:20: warning: no previous
prototype for '__delay' [-Wmissing-prototypes]
 extern inline void __delay(unsigned long loops)
./arch/microblaze/include/asm/delay.h:46:20: warning: no previous
prototype for '__udelay' [-Wmissing-prototypes]
 extern inline void __udelay(unsigned int x)
./arch/microblaze/include/asm/pgalloc.h:63:22: warning: no previous
prototype for 'get_pgd_slow' [-Wmissing-prototypes]
 extern inline pgd_t *get_pgd_slow(void)
./arch/microblaze/include/asm/pgalloc.h:73:22: warning: no previous
prototype for 'get_pgd_fast' [-Wmissing-prototypes]
 extern inline pgd_t *get_pgd_fast(void)
./arch/microblaze/include/asm/pgalloc.h:87:20: warning: no previous
prototype for 'free_pgd_fast' [-Wmissing-prototypes]
 extern inline void free_pgd_fast(pgd_t *pgd)
./arch/microblaze/include/asm/pgalloc.h:94:20: warning: no previous
prototype for 'free_pgd_slow' [-Wmissing-prototypes]
 extern inline void free_pgd_slow(pgd_t *pgd)
./arch/microblaze/include/asm/pgalloc.h:149:20: warning: no previous
prototype for 'pte_free_fast' [-Wmissing-prototypes]
 extern inline void pte_free_fast(pte_t *pte)
./arch/microblaze/include/asm/pgalloc.h:156:20: warning: no previous
prototype for 'pte_free_kernel' [-Wmissing-prototypes]
 extern inline void pte_free_kernel(struct mm_struct *mm, pte_t *pte)
./arch/microblaze/include/asm/pgalloc.h:161:20: warning: no previous
prototype for 'pte_free_slow' [-Wmissing-prototypes]
 extern inline void pte_free_slow(struct page *ptepage)

Signed-off-by: Michal Simek <michal.simek@xilinx.com>