powerpc: Remove in_kernel_text()

Last user of in_kernel_text() stopped using in with
commit 549e8152 ("powerpc: Make the 64-bit kernel as a
position-independent executable").

Generic function is_kernel_text() does the same.

So remote it.
Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/2a3a5b6f8cc0ef4e854d7b764f66aa8d2ee270d2.1624813698.git.christophe.leroy@csgroup.eu

arch/powerpc/include/asm/sections.h

@@ -38,14 +38,6 @@ extern char start_virt_trampolines[];
 extern char end_virt_trampolines[];
 #endif
 
-static inline int in_kernel_text(unsigned long addr)
-{
-	if (addr >= (unsigned long)_stext && addr < (unsigned long)__init_end)
-		return 1;
-
-	return 0;
-}
-
 static inline unsigned long kernel_toc_addr(void)
 {
 	/* Defined by the linker, see vmlinux.lds.S */