m68k: Remove never used asm/shm.h

m68k's asm/shm.h header has been part of the tree ever since m68k
support got added in v1.3.94. (It started as /include/asm-m68k/shm.h and
moved to its current location a few years ago.) It seems it was never
used: no file ever included it and nothing used the macros it defines.

(Actually, from v2.5.46 until v2.6.29-rc3 it was included by m68knommu's
asm/shm.h. But that header was just a very thin wrapper for this header
and was itself unused too.)

This header can safely be removed.
Signed-off-by: Paul Bolle <pebolle@tiscali.nl>
Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org>

arch/m68k/include/asm/shm.h

-#ifndef _M68K_SHM_H
-#define _M68K_SHM_H
-
-
-/* format of page table entries that correspond to shared memory pages
-   currently out in swap space (see also mm/swap.c):
-   bits 0-1 (PAGE_PRESENT) is  = 0
-   bits 8..2 (SWP_TYPE) are = SHM_SWP_TYPE
-   bits 31..9 are used like this:
-   bits 15..9 (SHM_ID) the id of the shared memory segment
-   bits 30..16 (SHM_IDX) the index of the page within the shared memory segment
-                    (actually only bits 25..16 get used since SHMMAX is so low)
-   bit 31 (SHM_READ_ONLY) flag whether the page belongs to a read-only attach
-*/
-/* on the m68k both bits 0 and 1 must be zero */
-/* format on the sun3 is similar, but bits 30, 31 are set to zero and all
-   others are reduced by 2. --m */
-
-#ifndef CONFIG_SUN3
-#define SHM_ID_SHIFT	9
-#else
-#define SHM_ID_SHIFT	7
-#endif
-#define _SHM_ID_BITS	7
-#define SHM_ID_MASK	((1<<_SHM_ID_BITS)-1)
-
-#define SHM_IDX_SHIFT	(SHM_ID_SHIFT+_SHM_ID_BITS)
-#define _SHM_IDX_BITS	15
-#define SHM_IDX_MASK	((1<<_SHM_IDX_BITS)-1)
-
-#endif /* _M68K_SHM_H */