sparc32: add irq + smp declarations to headers

In preparation for cleaning up a number of files add
declarations for irq and smp related data/functions to
the relevant headers.

This showed that the extern declaration of cputypval differed
in the two files where it was used.
As cputypval is defined like this:

cputypval:
        .asciz "sun4c"

the correct representation is a char array.
Fix users to use the new declaration.

Signed-off-by: Sam Ravnborg <sam@ravnborg.org>
Signed-off-by: David S. Miller <davem@davemloft.net>