riscv: fix KUnit test_kprobes crash when building with Clang

Clang misinterprets the placement of test_kprobes_addresses and
test_kprobes_functions arrays when they are not explicitly assigned
to a data section. This can lead to kmalloc_array() allocation
errors and KUnit failures.

When testing the Clang-compiled code in QEMU, this warning was emitted:

WARNING: CPU: 1 PID: 3000 at mm/page_alloc.c:5159 __alloc_frozen_pages_noprof+0xe6/0x2fc mm/page_alloc.c:5159

Further investigation revealed that the test_kprobes_addresses array
appeared to have over 100,000 elements, including invalid addresses;
whereas, according to test-kprobes-asm.S, test_kprobes_addresses
should only have 25 elements.

When compiling the kernel with GCC, the kernel boots correctly.

This patch fixes the issue by adding .section .rodata to explicitly
place arrays in the read-only data segment.

For detailed debug and analysis, see:
https://github.com/j1akai/temp/blob/main/20251113/readme.md

v1 -> v2：
- Drop changes to .align, and .globl.

Signed-off-by: Jiakai Xu <[e-mail]>
Signed-off-by: Jiakai Xu <[e-mail]>
Link: https://patch.msgid.link/[e-mail]
Link: https://github.com/llvm/llvm-project/issues/168308
Link: https://patch.msgid.link/[e-mail]
Signed-off-by: Paul Walmsley <[e-mail]>

arch/riscv/kernel/tests/kprobes/test-kprobes-asm.S

···
 
 #endif /* CONFIG_RISCV_ISA_C */
 
+.section .rodata
 SYM_DATA_START(test_kprobes_addresses)
 	RISCV_PTR test_kprobes_add_addr1
 	RISCV_PTR test_kprobes_add_addr2
···
 	RISCV_PTR 0
 SYM_DATA_END(test_kprobes_addresses)
 
+.section .rodata
 SYM_DATA_START(test_kprobes_functions)
 	RISCV_PTR test_kprobes_add
 	RISCV_PTR test_kprobes_jal