kernel: backport 4.18 patch adding DMI_PRODUCT_SKU

kernel: backport 4.18 patch adding DMI_PRODUCT_SKU

It's needed for applying some hardware quirks. This fixes:
drivers/net/wireless/broadcom/brcm80211/brcmfmac/dmi.c:60:20: error: 'DMI_PRODUCT_SKU' undeclared here (not in a function); did you mean 'DMI_PRODUCT_UUID'?
    DMI_EXACT_MATCH(DMI_PRODUCT_SKU, "T8"),

Fixes: 2cd234d96bd7 ("mac80211: brcm: backport remaining brcmfmac 5.2 patches")
Signed-off-by: Rafał Miłecki <rafal@milecki.pl>
(cherry picked from commit 4d11c4c3784196ed3e5b5a1f81fa415d99ef32b0)