firmware/dmi: Include product_sku info to modalias

BugLink: https://bugs.launchpad.net/bugs/1938143

Some Dell platforms rely on modalias to customize configuration,
the product sku can be more specific for the hardware.

Add product_sku to modalias for better utilization.

Signed-off-by: Kai-Chuan Hsieh <kaichuan.hsieh@canonical.com>
Signed-off-by: Jean Delvare <jdelvare@suse.de>
(cherry picked from commit e26f023)
Signed-off-by: Chia-Lin Kao (AceLan) <acelan.kao@canonical.com>

drivers/firmware/dmi-id.c

@@ -85,6 +85,7 @@ static ssize_t get_modalias(char *buffer, size_t buffer_size)
 		{ "svn", DMI_SYS_VENDOR },
 		{ "pn",  DMI_PRODUCT_NAME },
 		{ "pvr", DMI_PRODUCT_VERSION },
+		{ "sku", DMI_PRODUCT_SKU },
 		{ "rvn", DMI_BOARD_VENDOR },
 		{ "rn",  DMI_BOARD_NAME },
 		{ "rvr", DMI_BOARD_VERSION },