SiFive/U5SeriesPkg: Add CLINT to Device Tree

Add CLINT to Device Tree on U540 platform for
M-mode timer and IPI.

Cc: Sunil V L <sunilvl@ventanamicro.com>
Cc: Daniel Schaefer <daniel.schaefer@hpe.com>
Signed-off-by: Abner Chang <abner.chang@hpe.com>
Reviewed-by: Daniel Schaefer <daniel.schaefer@hpe.com>
Reviewed-by: Sunil V L <sunilvl@ventanamicro.com>