x86/microcode: Provide CONFIG_MICROCODE_INITRD32

Create an aggregate config switch which covers X86_32, MICROCODE and
BLK_DEV_INITRD to avoid lengthy #ifdeffery in upcoming code.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Link: https://lore.kernel.org/r/20231017211722.236208250@linutronix.de

arch/x86/Kconfig

@@ -1313,6 +1313,10 @@ config MICROCODE
 	def_bool y
 	depends on CPU_SUP_AMD || CPU_SUP_INTEL
 
+config MICROCODE_INITRD32
+	def_bool y
+	depends on MICROCODE && X86_32 && BLK_DEV_INITRD
+
 config MICROCODE_LATE_LOADING
 	bool "Late microcode loading (DANGEROUS)"
 	default n