powerpc/powernv: Remove pnv_eeh_cap_start()

This moves the logic of pnv_eeh_cap_start() to pnv_eeh_find_cap()
as the function is only called by pnv_eeh_find_cap(). The logic
of both functions are pretty simple. No need to have separate
functions.

Signed-off-by: Gavin Shan <gwshan@linux.vnet.ibm.com>
Reviewed-by: Andrew Donnellan <andrew.donnellan@au1.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>