b43: Fix 'me' -> 'be' typo in Kconfig

Also add a missing 'the' before 'runtime performance'.
Signed-off-by: NW. Trevor King <wking@tremily.us>
Signed-off-by: NJohn W. Linville <linville@tuxdriver.com>

drivers/net/wireless/b43/Kconfig

@@ -166,8 +166,8 @@ config B43_DEBUG
 	  Broadcom 43xx debugging.
 
 	  This adds additional runtime sanity checks and statistics to the driver.
-	  These checks and statistics might me expensive and hurt runtime performance
-	  of your system.
+	  These checks and statistics might be expensive and hurt the runtime
+	  performance of your system.
 	  This also adds the b43 debugfs interface.
 
 	  Do not enable this, unless you are debugging the driver.