thermal/intel_powerclamp: fix truncated kthread name

kthread name only allows 15 characters (TASK_COMMON_LEN is 16).
Thus rename the kthreads created by intel_powerclamp driver from
"kidle_inject/ + decimal cpuid" to "kidle_inj/ + decimal cpuid"
to avoid truncated kthead name for cpu 100 and later.

Signed-off-by: Zhang Rui <rui.zhang@intel.com>