drivers: net: Mark functions as static in 4965-debug.c

This patch marks the function il4965_ucode_rx_stats_read(),
il4965_ucode_tx_stats_read() and il4965_ucode_general_stats_read() in
4965-debug.c as static because they are not used outside this file.

Thus, it also removes the following warnings in
wireless/iwlegacy/4965-debug.c:

drivers/net/wireless/iwlegacy/4965-debug.c:59:1: warning: no previous prototype for ‘il4965_ucode_rx_stats_read’ [-Wmissing-prototypes]
drivers/net/wireless/iwlegacy/4965-debug.c:471:1: warning: no previous prototype for ‘il4965_ucode_tx_stats_read’ [-Wmissing-prototypes]
drivers/net/wireless/iwlegacy/4965-debug.c:637:1: warning: no previous prototype for ‘il4965_ucode_general_stats_read’ [-Wmissing-prototypes]

Signed-off-by: Rashika Kheria <rashika.kheria@gmail.com>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>
Signed-off-by: John W. Linville <linville@tuxdriver.com>