clk: renesas: Rename CLK_R8A7796 to CLK_R8A77960

Rename CONFIG_CLK_R8A7796 for R-Car M3-W (R8A77960) to
CONFIG_CLK_R8A77960, to avoid confusion with R-Car M3-W+ (R8A77961),
which will use CONFIG_CLK_R8A77961.

Based on Linux commit 92d1ebae9abf ("clk: renesas: Rename CLK_R8A7796
to CLK_R8A77960")

Reviewed-by: Marek Vasut <marek.vasut+renesas@mailbox.org>
Signed-off-by: Hai Pham <hai.pham.ud@renesas.com>
Signed-off-by: Marek Vasut <marek.vasut+renesas@mailbox.org>