riscv: Replace direct thread flag check with is_compat_task()

There is some code that detects compat mode into a task by checking the
flag directly, and other code that check using the helper is_compat_task().

Since the helper already exists, use it instead of checking the flags
directly.
Signed-off-by: Leonardo Bras <leobras@redhat.com>
Link: https://lore.kernel.org/r/20240103160024.70305-4-leobras@redhat.comSigned-off-by: Palmer Dabbelt <palmer@rivosinc.com>

arch/riscv/include/asm/elf.h

@@ -54,7 +54,7 @@ extern bool compat_elf_check_arch(Elf32_Ehdr *hdr);
 
 #ifdef CONFIG_64BIT
 #ifdef CONFIG_COMPAT
-#define STACK_RND_MASK		(test_thread_flag(TIF_32BIT) ? \
+#define STACK_RND_MASK		(is_compat_task() ? \
 				 0x7ff >> (PAGE_SHIFT - 12) : \
 				 0x3ffff >> (PAGE_SHIFT - 12))
 #else

arch/riscv/include/asm/pgtable.h

@@ -882,7 +882,7 @@ static inline pte_t pte_swp_clear_exclusive(pte_t pte)
 
 #ifdef CONFIG_COMPAT
 #define TASK_SIZE_32	(_AC(0x80000000, UL) - PAGE_SIZE)
-#define TASK_SIZE	(test_thread_flag(TIF_32BIT) ? \
+#define TASK_SIZE	(is_compat_task() ? \
 			 TASK_SIZE_32 : TASK_SIZE_64)
 #else
 #define TASK_SIZE	TASK_SIZE_64