sb/intel/ibexpeak: Fix enabling HPET

RCBA_HPTC needs to be read back to properly work.

This fixes SeaBIOS endlessly waiting for input instead of booting the
default entry. Linux already fixes this itself.

Change-Id: I22b8b34924f2add2185ec46470c1559bf2fb6d58
Signed-off-by: Arthur Heymans <arthur@aheymans.xyz>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/35757
Reviewed-by: Angel Pons <th3fanbus@gmail.com>
Reviewed-by: Patrick Rudolph <siro@das-labor.org>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>

src/southbridge/intel/ibexpeak/lpc.c

@@ -394,6 +394,7 @@ static void enable_hpet(void)
 	reg32 |= (1 << 7); // HPET Address Enable
 	reg32 &= ~(3 << 0);
 	RCBA32(HPTC) = reg32;
+	RCBA32(HPTC); /* Read back for it to work */
 
 	write32((u32 *)0xfed00010, read32((u32 *)0xfed00010) | 1);
 }