net: hsr: cosmetic: Remove extra white space

This change just removes extra (i.e. not needed) white space in
prp_drop_frame() function.

No functional changes.

Signed-off-by: Lukasz Majewski <lukma@denx.de>
Reviewed-by: Hangbin Liu <liuhangbin@gmail.com>
Link: https://lore.kernel.org/r/20240618125817.1111070-1-lukma@denx.de


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