core: fix typo in percpu read_mostly section

This fixes a typo that named the read_mostly section of percpu as
readmostly. It works fine with SMP because the linker script specifies
.data..percpu..readmostly. However, UP kernel builds don't have percpu
sections defined and the non-percpu version of the section is called
data..read_mostly, so .data..readmostly will float around and may break
things unexpectedly.

Looking at the original change that introduced data..percpu..readmostly
(commit c957ef2c), it looks like this
was the original intention.

Tested: Built UP kernel and confirmed the sections got merged.

- Before the patch:
$ objdump -h vmlinux.o  | grep '\.data\.\.read.*mostly'
38 .data..read_mostly 00004418  0000000000000000  0000000000000000  00431ac0  2**6
50 .data..readmostly 00000014  0000000000000000  0000000000000000  00444000  2**3

- After the patch:
$ objdump -h vmlinux.o  | grep '\.data\.\.read.*mostly'
38 .data..read_mostly 00004438  0000000000000000  0000000000000000  00431ac0  2**6
Signed-off-by: NZhengyu He <hzy@google.com>
Signed-off-by: NFilipe Brandenburger <filbranden@google.com>
Signed-off-by: NTejun Heo <tj@kernel.org>

include/asm-generic/vmlinux.lds.h

@@ -693,7 +693,7 @@
 	. = ALIGN(PAGE_SIZE);						\
 	*(.data..percpu..page_aligned)					\
 	. = ALIGN(cacheline);						\
-	*(.data..percpu..readmostly)					\
+	*(.data..percpu..read_mostly)					\
 	. = ALIGN(cacheline);						\
 	*(.data..percpu)						\
 	*(.data..percpu..shared_aligned)				\

include/linux/percpu-defs.h

@@ -146,10 +146,10 @@
  * Declaration/definition used for per-CPU variables that must be read mostly.
  */
 #define DECLARE_PER_CPU_READ_MOSTLY(type, name)			\
-	DECLARE_PER_CPU_SECTION(type, name, "..readmostly")
+	DECLARE_PER_CPU_SECTION(type, name, "..read_mostly")
 
 #define DEFINE_PER_CPU_READ_MOSTLY(type, name)				\
-	DEFINE_PER_CPU_SECTION(type, name, "..readmostly")
+	DEFINE_PER_CPU_SECTION(type, name, "..read_mostly")
 
 /*
  * Intermodule exports for per-CPU variables.  sparse forgets about