conf/machine/: fix configuration for Strongarm devices

conf/machine/: fix configuration for Strongarm devices
* replace erroneous TARGET_CC_ARCH line optimising for xscale instead of strongarm
* remove inclusion of tune-strongarm.inc from collie.conf and replace it with the
  correct TARGET_CC_ARCH.  Collie is the only Strongarm 1110 device in OE and thus
  needs special treatment
* rename tune-strongarm.inc to tune-strongarm1100.inc and leave a short note to
  make it clear the file only applies to Strongarm 1100 devices.