use BIT() macro instead of explicit shifts

As a side effect, the BIT() macro creates a word_t instead of an int,
so it can can handle even shift that exceed the int limits. This makes
the code more robust and provides the preferred coding pattern.

Signed-off-by: Axel Heider <axelheider@gmx.de>

src/arch/arm/machine/hardware.c

@@ -34,7 +34,7 @@ BOOT_CODE void map_kernel_devices(void)
         if (!kernel_devices[i].userAvailable) {
             p_region_t reg = {
                 .start = kernel_devices[i].paddr,
-                .end = kernel_devices[i].paddr + (1 << PAGE_BITS),
+                .end = kernel_devices[i].paddr + BIT(PAGE_BITS),
             };
             reserve_region(reg);
         }

src/arch/riscv/machine/hardware.c

@@ -50,7 +50,7 @@ BOOT_CODE void map_kernel_devices(void)
         if (!kernel_devices[i].userAvailable) {
             p_region_t reg = {
                 .start = kernel_devices[i].paddr,
-                .end = kernel_devices[i].paddr + (1 << seL4_LargePageBits),
+                .end = kernel_devices[i].paddr + BIT(seL4_LargePageBits),
             };
             reserve_region(reg);
         }