clk: renesas: cpg-mssr: Simplify pointer math in cpg_rzt2h_mstp_read()

clk: renesas: cpg-mssr: Simplify pointer math in cpg_rzt2h_mstp_read()

Private state is available in all places where cpg_rzt2h_mstp_read() is
called, remove the extra pointer math used to find it from clk_hw.

While at it, put these statements on a single line as they do not exceed
the 80 columns limit.

Signed-off-by: Cosmin Tanislav <cosmin-gabriel.tanislav.xa@renesas.com>
Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
Link: https://patch.msgid.link/20251127145654.3253992-2-cosmin-gabriel.tanislav.xa@renesas.com
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>