staging: r8188eu: the bcnhead parameter is always 0

The only caller of efuse_read_phymap_from_txpktbuf sets bcnhead to 0.
Remove this function parameter and simplify the function body.

Signed-off-by: Martin Kaiser <martin@kaiser.cx>
Link: https://lore.kernel.org/r/20220709171000.180481-15-martin@kaiser.cx


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