refactor(memory share): use UART macro in device mem share

Remove hard coded UART address in the device memory sharing
test by using the PLAT_ARM_UART_BASE macro.

Signed-off-by: Daniel Boulby <daniel.boulby@arm.com>
Change-Id: Ie83e2ff7a41379361018e44d4c6f71198c07e15a
1 file changed