staging: rtl8723bs: Rename 'Hal8723BPhyCfg.h' using snake case.

Camel-case is discouraged in the linux kernel coding style.  Rename
this header file using snake case instead.

Signed-off-by: Quytelda Kahja <quytelda@tamalin.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>