ARC-setup: Use seq_putc() in show_cpuinfo()

[SF Markus Elfring]

>> A single character (line break) should be put into a sequence.
>> Thus use the corresponding function "seq_putc".
> 
> Perhaps reword the changelog to say that seqc_putc is more efficient than
> seqc_printf to output a single char.
> I mean _printf is not wrong but not as efficient ?

I came along source files for a few other software modules with similar
change possibilities.
Unfortunately, the corresponding developers are not convinced yet
to replace a call of the function "seq_printf" at the end by
a "seq_putc" because of software efficiency reasons.

Do you find this update suggestion acceptable to some degree
for the function "setup"?

Regards,
Markus