staging: r8188eu: rtl8188e_EfuseGetCurrentSize is now unused

After we removed efuse write support, rtl8188e_EfuseGetCurrentSize is no
longer needed. Remove this function and its internal helpers.

Signed-off-by: Martin Kaiser <martin@kaiser.cx>
Link: https://lore.kernel.org/r/20211113185518.23941-6-martin@kaiser.cx


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