Simplify math to caluclate the page count for the ramdisk

Rather than replace range_inclusive, we can remove the nesting doll math from ramdisk_page_count instead.
IMO this makes the code a bit more readable.

Author: jasoncouture

common/src/lib.rs

@@ -298,7 +298,7 @@ where
         let physical_address = PhysAddr::new(ramdisk_address);
         let ramdisk_physical_start_page: PhysFrame<Size4KiB> =
             PhysFrame::containing_address(physical_address);
-        let ramdisk_page_count = ((system_info.ramdisk_len - 1) / Size4KiB::SIZE) + 1;
+        let ramdisk_page_count = system_info.ramdisk_len / Size4KiB::SIZE;
         let ramdisk_physical_end_page = ramdisk_physical_start_page + ramdisk_page_count;
         let start_page = Page::from_start_address(ramdisk_address_start)
             .expect("the ramdisk start address must be page aligned");