Revert "timers: Rename del_timer_sync() to timer_delete_sync()"

This reverts commit df420917 which is
commit 9b13df3fb64ee95e2397585404e442afee2c7d4f upstream.

It breaks the Android kernel abi by turning del_timer_sync() into an
inline function, which breaks the abi.  Fix this by putting it back as
needed AND fix up the only use of this new function in
drivers/net/wireless/broadcom/brcm80211/brcmfmac/cfg80211.c which is
what caused this commit to be backported to 5.4.274 in the first place.

Bug: 161946584
Change-Id: Icd26c7c81e6172f36eeeb69827989bfab1d32afe
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>