qca_spi: Make interrupt remembering atomic

The whole mechanism to remember occurred SPI interrupts is not atomic,
which could lead to unexpected behavior. So fix this by using atomic bit
operations instead.

Fixes: 291ab06e

 ("net: qualcomm: new Ethernet over SPI driver for QCA7000")
Signed-off-by: Stefan Wahren <wahrenst@gmx.net>
Link: https://lore.kernel.org/r/20240614145030.7781-1-wahrenst@gmx.net
Signed-off-by: Paolo Abeni <pabeni@redhat.com>