tspdrv: Add a sysfs control for timed vibrator strength

Change-Id: I66dec312e52a3c8834a93f6b8970c94a0d6af923
arch/arm/Makefile: Enable pipe compiling

-pipe

Use pipes rather than temporary files for communication between the various stages of
compilation. This fails to work on some systems where the assembler is unable to read
from a pipe; but the GNU assembler has no trouble.