i3c: master: no need to iterate master device twice

We already have the master device in a variable, reuse it.

Signed-off-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
Acked-by: Vitor Soares <vitor.soares@synopsys.com>
Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Boris Brezillon <boris.brezillon@collabora.com>
Link: https://lore.kernel.org/linux-i3c/20200214145853.24762-1-wsa+renesas@sang-engineering.com