staging: r8188eu: use ieee80211 define for fragment number

Use the IEEE80211_SCTL_FRAG define to extract the fragment number from an
incoming frame.

pattrib->frag_num must be in host endianness, we have to convert
hdr->seq_ctrl, this field is little-endian.

Remove the local GetFragNum macro, it is not used any more.
Signed-off-by: Martin Kaiser <martin@kaiser.cx>
Link: https://lore.kernel.org/r/20220327180944.712545-10-martin@kaiser.cxSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/r8188eu/core/rtw_recv.c

@@ -1077,7 +1077,7 @@ static int validate_recv_frame(struct adapter *adapter, struct recv_frame *precv
 
 	pattrib->to_fr_ds = get_tofr_ds(ptr);
 
-	pattrib->frag_num = GetFragNum(ptr);
+	pattrib->frag_num = le16_to_cpu(hdr->seq_ctrl) & IEEE80211_SCTL_FRAG;
 	pattrib->seq_num = IEEE80211_SEQ_TO_SN(le16_to_cpu(hdr->seq_ctrl));
 
 	pattrib->pw_save = ieee80211_has_pm(hdr->frame_control);

drivers/staging/r8188eu/include/wifi.h

@@ -189,9 +189,6 @@ enum WIFI_REG_DOMAIN {
 		*(__le16 *)(pbuf) |= cpu_to_le16(type); \
 	} while (0)
 
-#define GetFragNum(pbuf)			\
-	(le16_to_cpu(*(__le16 *)((size_t)(pbuf) + 22)) & 0x0f)
-
 #define GetTupleCache(pbuf)			\
 	(cpu_to_le16(*(unsigned short *)((size_t)(pbuf) + 22)))