RISC-V: Remove unnecessary include from compat.h

RISC-V: Remove unnecessary include from compat.h

Without this I get a bunch of build errors like

    In file included from ./include/linux/sched/task_stack.h:12,
                     from ./arch/riscv/include/asm/compat.h:12,
                     from ./arch/riscv/include/asm/pgtable.h:115,
                     from ./include/linux/pgtable.h:6,
                     from ./include/linux/mm.h:30,
                     from arch/riscv/kernel/asm-offsets.c:8:
    ./include/linux/kasan.h:50:37: error: ‘MAX_PTRS_PER_PTE’ undeclared here (not in a function); did you mean ‘PTRS_PER_PTE’?
       50 | extern pte_t kasan_early_shadow_pte[MAX_PTRS_PER_PTE + PTE_HWTABLE_PTRS];
          |                                     ^~~~~~~~~~~~~~~~
          |                                     PTRS_PER_PTE
    ./include/linux/kasan.h:51:8: error: unknown type name ‘pmd_t’; did you mean ‘pgd_t’?
       51 | extern pmd_t kasan_early_shadow_pmd[MAX_PTRS_PER_PMD];
          |        ^~~~~
          |        pgd_t
    ./include/linux/kasan.h:51:37: error: ‘MAX_PTRS_PER_PMD’ undeclared here (not in a function); did you mean ‘PTRS_PER_PGD’?
       51 | extern pmd_t kasan_early_shadow_pmd[MAX_PTRS_PER_PMD];
          |                                     ^~~~~~~~~~~~~~~~
          |                                     PTRS_PER_PGD
    ./include/linux/kasan.h:52:8: error: unknown type name ‘pud_t’; did you mean ‘pgd_t’?
       52 | extern pud_t kasan_early_shadow_pud[MAX_PTRS_PER_PUD];
          |        ^~~~~
          |        pgd_t
    ./include/linux/kasan.h:52:37: error: ‘MAX_PTRS_PER_PUD’ undeclared here (not in a function); did you mean ‘PTRS_PER_PGD’?
       52 | extern pud_t kasan_early_shadow_pud[MAX_PTRS_PER_PUD];
          |                                     ^~~~~~~~~~~~~~~~
          |                                     PTRS_PER_PGD
    ./include/linux/kasan.h:53:8: error: unknown type name ‘p4d_t’; did you mean ‘pgd_t’?
       53 | extern p4d_t kasan_early_shadow_p4d[MAX_PTRS_PER_P4D];
          |        ^~~~~
          |        pgd_t
    ./include/linux/kasan.h:53:37: error: ‘MAX_PTRS_PER_P4D’ undeclared here (not in a function); did you mean ‘PTRS_PER_PGD’?
       53 | extern p4d_t kasan_early_shadow_p4d[MAX_PTRS_PER_P4D];
          |                                     ^~~~~~~~~~~~~~~~
          |                                     PTRS_PER_PGD

Link: https://lore.kernel.org/r/20241126143250.29708-1-palmer@rivosinc.com
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>