ieee1394: fix broken signed char assumption.
ieee1394: fix broken signed char assumption.

"ack_code" is assigned (and tested against) negative numbers, but was
declared as "char".  Which only works if "char" is signed - which it
necessarily isn't.

So make that signedness assumption specific.

KristFoundation/Programs,TeamVee-Kanas/android_kernel_samsung_kanas,KristFoundation/Programs,KristFoundation/Programs,TeamVee-Kanas/android_kernel_samsung_kanas,KristFoundation/Programs,TeamVee-Kanas/android_kernel_samsung_kanas,KristFoundation/Programs,TeamVee-Kanas/android_kernel_samsung_kanas,TeamVee-Kanas/android_kernel_samsung_kanas,KristFoundation/Programs