lib: Fix ia64 bootloader linkage

kbuild robot reports that since commit ce76d938 ("lib: Add memcat_p():
paste 2 pointer arrays together") the ia64/hp/sim/boot fails to link:

> LD      arch/ia64/hp/sim/boot/bootloader
> lib/string.o: In function `__memcat_p':
> string.c:(.text+0x1f22): undefined reference to `__kmalloc'
> string.c:(.text+0x1ff2): undefined reference to `__kmalloc'
> make[1]: *** [arch/ia64/hp/sim/boot/Makefile:37: arch/ia64/hp/sim/boot/bootloader] Error 1

The reason is, the above commit, via __memcat_p(), adds a call to
__kmalloc to string.o, which happens to be used in the bootloader, but
there's no kmalloc or slab or anything.

Since the linker would only pull in objects that contain referenced
symbols, moving __memcat_p() to a different compilation unit solves the
problem.

Fixes: ce76d938 ("lib: Add memcat_p(): paste 2 pointer arrays together")
Signed-off-by: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Reported-by: kbuild test robot <lkp@intel.com>
Cc: Fenghua Yu <fenghua.yu@intel.com>
Cc: Tony Luck <tony.luck@intel.com>
Cc: Joe Perches <joe@perches.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>