brcmfmac: remove set but not used variable 'mpnum','nsp','nmp'

Fixes gcc '-Wunused-but-set-variable' warning:

drivers/net/wireless/broadcom/brcm80211/brcmfmac/chip.c: In function brcmf_chip_dmp_get_regaddr:
drivers/net/wireless/broadcom/brcm80211/brcmfmac/chip.c:790:5: warning: variable mpnum set but not used [-Wunused-but-set-variable]
drivers/net/wireless/broadcom/brcm80211/brcmfmac/chip.c: In function brcmf_chip_dmp_erom_scan:
drivers/net/wireless/broadcom/brcm80211/brcmfmac/chip.c:866:10: warning: variable nsp set but not used [-Wunused-but-set-variable]
drivers/net/wireless/broadcom/brcm80211/brcmfmac/chip.c: In function brcmf_chip_dmp_erom_scan:
drivers/net/wireless/broadcom/brcm80211/brcmfmac/chip.c:866:5: warning: variable nmp set but not used [-Wunused-but-set-variable]

Reported-by: Hulk Robot <hulkci@huawei.com>
Signed-off-by: zhengbin <zhengbin13@huawei.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>