mb/*/*/Kconfig: Drop redundant redeclaration of MAINBOARD_VENDOR

Change-Id: Ic92e08ae5b741889a8200d10ea8148e4b4384dc8
Signed-off-by: Arthur Heymans <arthur@aheymans.xyz>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/37270
Reviewed-by: HAOUAS Elyes <ehaouas@noos.fr>
Reviewed-by: David Guckian
Reviewed-by: Angel Pons <th3fanbus@gmail.com>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>

src/mainboard/intel/strago/Kconfig

@@ -30,10 +30,6 @@ config MAINBOARD_PART_NUMBER
 	string
 	default "Strago"
 
-config MAINBOARD_VENDOR
-	string
-	default "Intel"
-
 config VGA_BIOS_FILE
 	string
 	depends on VGA_BIOS