wic: Rename partitions as per the x-wic.inc changes

x-boot - boot
x-sys-a - sys-a
x-sys-b - sys-b
x-dev-data - devdata
x-sys-data - sysdata
x-app-data - appdata

Signed-off-by: Andrei Gherzan <andrei.gherzan@huawei.com>