i2c: core: apply 'is_suspended' check for SMBus, too

We checked I2C calls, but not SMBus. Refactor the helper to an inline
function and use it for both, I2C and SMBus.

Fixes: 9ac6cb5f ("i2c: add suspended flag and accessors for i2c adapters")
Reported-by: Peter Rosin <peda@axentia.se>
Signed-off-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
Reviewed-by: Simon Horman <horms+renesas@verge.net.au>
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>