spi: sh_qspi: Drop SPBDCR wait

Waiting for SPBDCR == 1 is not required and is covered by the
subsequent wait for SPSR_SPRFF, so drop this.

Signed-off-by: Marek Vasut <marek.vasut+renesas@gmail.com>
Cc: Nobuhiro Iwamatsu <nobuhiro.iwamatsu.yj@renesas.com>