rtlwifi: rtl818x: constify local structures

rtlwifi: rtl818x: constify local structures

For structure types defined in the same file or local header files, find
top-level static structure declarations that have the following
properties:
1. Never reassigned.
2. Address never taken
3. Not passed to a top-level macro call
4. No pointer or array-typed field passed to a function or stored in a
variable.
Declare structures having all of these properties as const.

Done using Coccinelle.
Based on a suggestion by Joe Perches <[email protected]>.

Signed-off-by: Julia Lawall <[email protected]>
Signed-off-by: Kalle Valo <[email protected]>