sparc: correct section of current_pc()

Latest mainline gives this section mismatch on sparc:

The function current_pc() references
the variable __init no_sun4u_here.
This is often because current_pc lacks a __init
annotation or the annotation of no_sun4u_here is wrong.

Since current_pc() is used only in early time, it is correct to
put it in .init section.

Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>