linux-wandboard

powerpc/44x: Fix build error with -Werror for Warp platform

With -Werror enabled during the build, the warp.c file fails to build
due to the temp_isr function not containing a return statement.  This
fixes the build error and documents that the function never returns.

Signed-off-by: Josh Boyer <jwboyer@linux.vnet.ibm.com>