staging: rtl8188eu: ctrl vendor req value is always 0x05

The bRequest value for the vendor specific control requests sent by this
driver is always 0x05. Replace the function parameter with a define. Use
the same define as the rtlwifi driver.

Signed-off-by: Martin Kaiser <martin@kaiser.cx>
Link: https://lore.kernel.org/r/20210406204829.18130-2-martin@kaiser.cx


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