einj_mem_uc: Fix parsing of available_error_types

Commit 38f47153c2c1 ("Check the injected error type available before
write error type") didn't skip the extra text on the end of each line
when checking whether a specific error type is supported.

Reported-by: Liu Xinpeng <liuxp11@chinatelecom.cn>
Signed-off-by: Tony Luck <tony.luck@intel.com>