wifi: ipw2x00: remove unused _ipw_read16 function

clang with W=1 reports
drivers/net/wireless/intel/ipw2x00/ipw2200.c:381:19: error:
  unused function '_ipw_read16' [-Werror,-Wunused-function]
static inline u16 _ipw_read16(struct ipw_priv *ipw, unsigned long ofs)
                  ^
This function and its wrapping marco are not used, so remove them.
Signed-off-by: Tom Rix <trix@redhat.com>
Signed-off-by: Kalle Valo <kvalo@kernel.org>
Link: https://lore.kernel.org/r/20230319135418.1703380-1-trix@redhat.com

drivers/net/wireless/intel/ipw2x00/ipw2200.c

@@ -377,19 +377,6 @@ static inline u8 _ipw_read8(struct ipw_priv *ipw, unsigned long ofs)
 	_ipw_read8(ipw, ofs); \
 })
 
-/* 16-bit direct read (low 4K) */
-static inline u16 _ipw_read16(struct ipw_priv *ipw, unsigned long ofs)
-{
-	return readw(ipw->hw_base + ofs);
-}
-
-/* alias to 16-bit direct read (low 4K of SRAM/regs), with debug wrapper */
-#define ipw_read16(ipw, ofs) ({ \
-	IPW_DEBUG_IO("%s %d: read_direct16(0x%08X)\n", __FILE__, __LINE__, \
-			(u32)(ofs)); \
-	_ipw_read16(ipw, ofs); \
-})
-
 /* 32-bit direct read (low 4K) */
 static inline u32 _ipw_read32(struct ipw_priv *ipw, unsigned long ofs)
 {