[ch6][fix]fix round up error during data block allocation#6

0x822a5b87 wants to merge 1 commit intoLearningOS:ch6LearningOS/os-rcore-classroom-2025a-rcore-rCore-Tutorial-Code:ch6from

0x822a5b87:ch60x822a5b87/os-rcore-classroom-2025a-rcore-rCore-Tutorial-Code:ch6Copy head branch name to clipboard