staging: rtl8188eu: make efuse_ReadEFuse static

The function is used only inside rtw_efuse.c.

Signed-off-by: Martin Kaiser <martin@kaiser.cx>
Link: https://lore.kernel.org/r/20210620175301.14988-11-martin@kaiser.cx


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