RAS/CEC: Use the right length for "cec_disable"

parse_cec_param() compares a string with "cec_disable" using only 7
characters of the 11-character-long string.

The proper solution for this would be:

#define CEC_DISABLE 	"cec_disable"

	strncmp(str, CEC_DISABLE, strlen(CEC_DISABLE))

but when comparing a string against a string constant strncmp() has no
advantage over strcmp() because the comparison is guaranteed to be bound by
the string constant. So just replace str strncmp() with strcmp().

[ tglx: Made it use strcmp and updated the changelog ]

Fixes: 011d8261 ("RAS: Add a Corrected Errors Collector")
Signed-off-by: Nicolas Iooss <nicolas.iooss_linux@m4x.org>
Signed-off-by: Borislav Petkov <bp@suse.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: stable@vger.kernel.org
Link: http://lkml.kernel.org/r/20170903075440.30250-1-nicolas.iooss_linux@m4x.org