src: change coreboot to lowercase

The word 'coreboot' should always be written in lowercase, even at the
start of a sentence.

Change-Id: I7945ddb988262e7483da4e623cedf972380e65a2
Signed-off-by: Martin Roth <martinroth@google.com>
Reviewed-on: https://review.coreboot.org/20029
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Philippe Mathieu-Daudé <philippe.mathieu.daude@gmail.com>
Reviewed-by: Patrick Georgi <pgeorgi@google.com>

src/soc/intel/skylake/cpu.c

@@ -226,7 +226,7 @@ static void configure_isst(void)
 	if (conf->speed_shift_enable) {
 		/*
 		* Kernel driver checks CPUID.06h:EAX[Bit 7] to determine if HWP
-		  is supported or not. Coreboot needs to configure MSR 0x1AA
+		  is supported or not. coreboot needs to configure MSR 0x1AA
 		  which is then reflected in the CPUID register.
 		*/
 		msr = rdmsr(MSR_MISC_PWR_MGMT);