staging: r8188eu: remove two unused defines

The C2H_MEM_SZ and FREE_CMDOBJ_SZ defines are not used by the r8188eu
driver. Remove them.

Signed-off-by: Martin Kaiser <martin@kaiser.cx>
Tested-by: Philipp Hortmann <philipp.g.hortmann@gmail.com> # Edimax N150
Link: https://lore.kernel.org/r/20221015151115.232095-7-martin@kaiser.cx


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>