move libgcc.h to include/linux

Introducing a new include/lib directory just for this file totally
messes up tab completion for include/linux, which is highly annoying.

Move it to include/linux where we have headers for all kinds of other
lib/ code as well.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Palmer Dabbelt <palmer@sifive.com>

lib/ashldi3.c

@@ -16,7 +16,7 @@
 
 #include <linux/export.h>
 
-#include <lib/libgcc.h>
+#include <linux/libgcc.h>
 
 long long notrace __ashldi3(long long u, word_type b)
 {

lib/ashrdi3.c

@@ -16,7 +16,7 @@
 
 #include <linux/export.h>
 
-#include <lib/libgcc.h>
+#include <linux/libgcc.h>
 
 long long notrace __ashrdi3(long long u, word_type b)
 {

lib/cmpdi2.c

@@ -16,7 +16,7 @@
 
 #include <linux/export.h>
 
-#include <lib/libgcc.h>
+#include <linux/libgcc.h>
 
 word_type notrace __cmpdi2(long long a, long long b)
 {

lib/lshrdi3.c

@@ -17,7 +17,7 @@
  */
 
 #include <linux/module.h>
-#include <lib/libgcc.h>
+#include <linux/libgcc.h>
 
 long long notrace __lshrdi3(long long u, word_type b)
 {

lib/muldi3.c

@@ -15,7 +15,7 @@
  */
 
 #include <linux/export.h>
-#include <lib/libgcc.h>
+#include <linux/libgcc.h>
 
 #define W_TYPE_SIZE 32
 

lib/ucmpdi2.c

@@ -15,7 +15,7 @@
  */
 
 #include <linux/module.h>
-#include <lib/libgcc.h>
+#include <linux/libgcc.h>
 
 word_type __ucmpdi2(unsigned long long a, unsigned long long b)
 {