staging: rtl8192u: Fix variable shadowing warning

staging: rtl8192u: Fix variable shadowing warning

Fixes the following sparse warnings:

drivers/staging/rtl8192u/r8192U_core.c:2306:21: warning: symbol 'i' shadows an earlier one
drivers/staging/rtl8192u/r8192U_core.c:2254:13: originally declared here
drivers/staging/rtl8192u/r8192U_core.c:2371:29: warning: symbol 'i' shadows an earlier one
drivers/staging/rtl8192u/r8192U_core.c:2254:13: originally declared here

Signed-off-by: Cláudio Maia <clrrm@isep.ipp.pt>
Link: https://lore.kernel.org/r/20210514230459.15752-1-clrrm@isep.ipp.pt
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>