ath5k: Remove unused BUG_ON

Clang warns that the address of a pointer will always evaluated as true
in a boolean context:

drivers/net/wireless/ath/ath5k/debug.c:1031:14: warning: address of
array 'ah->sbands' will always evaluate to 'true'
[-Wpointer-bool-conversion]
        BUG_ON(!ah->sbands);
               ~~~~~^~~~~~
./include/asm-generic/bug.h:61:45: note: expanded from macro 'BUG_ON'
#define BUG_ON(condition) do { if (unlikely(condition)) BUG(); } while (0)
                                            ^~~~~~~~~
./include/linux/compiler.h:77:42: note: expanded from macro 'unlikely'
# define unlikely(x)    __builtin_expect(!!(x), 0)
                                            ^
1 warning generated.

Given that this condition is always false because of the logical not,
just remove it.

Link: https://github.com/ClangBuiltLinux/linux/issues/130
Signed-off-by: Nathan Chancellor <natechancellor@gmail.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>

drivers/net/wireless/ath/ath5k/debug.c

@@ -1028,8 +1028,6 @@ ath5k_debug_dump_bands(struct ath5k_hw *ah)
 	if (likely(!(ah->debug.level & ATH5K_DEBUG_DUMPBANDS)))
 		return;
 
-	BUG_ON(!ah->sbands);
-
 	for (b = 0; b < NUM_NL80211_BANDS; b++) {
 		struct ieee80211_supported_band *band = &ah->sbands[b];
 		char bname[6];