brcm80211: fmac: move packet realloc stats to struct brcmf_bus

brcm80211: fmac: move packet realloc stats to struct brcmf_bus

tx_realloc is used by both common layer and bus layer. This patch
moves it to interface structure brcmf_bus as part of the fullmac
bus interface refactoring.

Reviewed-by: Pieter-Paul Giesberts <pieterpg@broadcom.com>
Reviewed-by: Arend van Spriel <arend@broadcom.com>
Reviewed-by: Alwin Beukers <alwin@broadcom.com>
Signed-off-by: Franky Lin <frankyl@broadcom.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>