staging: r8188eu: merge three small functions

ReadAdapterInfo8188EU calls _ReadAdapterInfo8188EU.
_ReadAdapterInfo8188EU calls _ReadPROMContent.

Each of these functions is small and has only one caller. Move all
their code into ReadAdapterInfo8188EU.

Signed-off-by: Martin Kaiser <martin@kaiser.cx>
Link: https://lore.kernel.org/r/20211111212644.9011-6-martin@kaiser.cx


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