staging:rtl8192u: Remove unused RTL8190_CPU_START_OFFSET - Style

The defined constant RTL8190_CPU_START_OFFSET is not used in the code
so has been removed. This is a coding style change which should have
no impact on runtime code execution.

Signed-off-by: John Whitmore <johnfwhitmore@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>