riscv: drop the use of XIP_OFFSET in kernel_mapping_va_to_pa()

XIP_OFFSET is the hard-coded offset of writable data section within the
kernel.

By hard-coding this value, the read-only section of the kernel (which is
placed before the writable data section) is restricted in size.

As a preparation to remove this hard-coded macro XIP_OFFSET entirely,
remove the use of XIP_OFFSET in kernel_mapping_va_to_pa(). The macro
XIP_OFFSET is used in this case to check if the virtual address is mapped
to Flash or to RAM. The same check can be done with kernel_map.xiprom_sz.
Signed-off-by: Nam Cao <namcao@linutronix.de>
Reviewed-by: Alexandre Ghiti <alexghiti@rivosinc.com>
Link: https://lore.kernel.org/r/644c13d9467525a06f5d63d157875a35b2edb4bc.1717789719.git.namcao@linutronix.deSigned-off-by: Palmer Dabbelt <palmer@rivosinc.com>

arch/riscv/include/asm/page.h

@@ -159,7 +159,7 @@ phys_addr_t linear_mapping_va_to_pa(unsigned long x);
 #ifdef CONFIG_XIP_KERNEL
 #define kernel_mapping_va_to_pa(y) ({						\
 	unsigned long _y = (unsigned long)(y);					\
-	(_y < kernel_map.virt_addr + XIP_OFFSET) ?				\
+	(_y < kernel_map.virt_addr + kernel_map.xiprom_sz) ?			\
 		(_y - kernel_map.va_kernel_xip_text_pa_offset) :		\
 		(_y - kernel_map.va_kernel_xip_data_pa_offset);			\
 	})