jetway/nf81-t56n-lf: Simplify agesawrapper_amdinitcpuio()

Follow same reasoning as:
12fd779 hp/pavilion_m6_1035dx: Simplify agesawrapper_amdinitcpuio()
Use coreboot variants for PCI and MSR access over AGESA's.

Change-Id: Ic0d8bbd0faf6423605567564ad216b79e1331cc9
Signed-off-by: Edward O'Callaghan <eocallaghan@alterapraxis.com>
Reviewed-on: http://review.coreboot.org/5472
Tested-by: build bot (Jenkins)
Reviewed-by: Alexandru Gagniuc <mr.nuke.me@gmail.com>