i2c: busses: replace spin_lock_irqsave by spin_lock in hard IRQ

The code has been in a irq-disabled context since it is hard IRQ. There
is no necessity to do it again.

Signed-off-by: Barry Song <song.bao.hua@hisilicon.com>
Reviewed-by: Akash Asthana <akashast@codeaurora.org>
Reviewed-by: Mukesh Kumar Savaliya <msavaliy@codeaurora.org>
Signed-off-by: Wolfram Sang <wsa@kernel.org>