selftests: net: Correct couple of spelling mistakes

Changes :
	- "excercise" is corrected to "exercise" in drivers/net/mlxsw/spectrum-2/tc_flower.sh
	- "mutliple" is corrected to "multiple" in drivers/net/netdevsim/ethtool-fec.sh

Signed-off-by: Prabhav Kumar Vaish <pvkumar5749404@gmail.com>
Reviewed-by: Jiri Pirko <jiri@nvidia.com>
Link: https://lore.kernel.org/r/20240228120701.422264-1-pvkumar5749404@gmail.com


Signed-off-by: Jakub Kicinski <kuba@kernel.org>