Staging: winbond: Made local functions static

Few functions are used only in one file. They are not included in any
other .h or .c files (I used grep to check). They seem to be local functions.
So, I have made them static.
I have also inlined one function as it is a one line function.

Signed-off-by: Harsh Kumar <harsh1kumar@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>