spi: lantiq: remove redundant irqsave and irqrestore in hardIRQ

Running in hardIRQ, disabling irq is redundant.

Signed-off-by: Barry Song <song.bao.hua@hisilicon.com>
Link: https://lore.kernel.org/r/20200916101042.21860-1-song.bao.hua@hisilicon.com
Signed-off-by: Mark Brown <broonie@kernel.org>