external/gard: Make use of the common/ flash reading code
external/gard: Make use of the common/ flash reading code

Signed-off-by: Cyril Bur <6ce38dade8c4b52fd55c193fae70fd1d1275c3c3@au1.ibm.com>
Reviewed-by: Alistair Popple <e9adbcf81c8a36ccc628e09bc92d0e25e1c8e501@popple.id.au>
Signed-off-by: Stewart Smith <ec31ab75ddf977353c8f660f92ea8b23f64aef25@linux.vnet.ibm.com>

mikey/skiboot,qemu/skiboot,stewart-ibm/skiboot,open-power/skiboot,open-power/skiboot,mikey/skiboot,qemu/skiboot,legoater/skiboot,open-power/skiboot,csmart/skiboot,mikey/skiboot,shenki/skiboot,open-power/skiboot,qemu/skiboot,shenki/skiboot,qemu/skiboot,legoater/skiboot,shenki/skiboot,legoater/skiboot,legoater/skiboot,qemu/skiboot,stewart-ibm/skiboot,shenki/skiboot,shenki/skiboot,csmart/skiboot,csmart/skiboot,stewart-ibm/skiboot,open-power/skiboot,legoater/skiboot