staging: rtl8192e: Remove u4RegValue which is always zero

As the array antenna_tx_pwr_diff is always zero, u4RegValue is always set
to zero. Replace u4RegValue to avoid CamelCase which is not accepted by
checkpatch.

Signed-off-by: Philipp Hortmann <philipp.g.hortmann@gmail.com>
Link: https://lore.kernel.org/r/2aa104c0f7a5cede7eea289fe92390295592b0e9.1674244819.git.philipp.g.hortmann@gmail.com


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