I386: fix signedness mismatch warning

&i386_regs.esp is a pointer to long, not unsigned long.
It needs a cast.

Signed-off-by: Denys Vlasenko <dvlasenk@redhat.com>
diff --git a/syscall.c b/syscall.c
index 02c0867..1b49bb3 100644
--- a/syscall.c
+++ b/syscall.c
@@ -678,7 +678,8 @@
 
 #if defined(I386)
 static struct user_regs_struct i386_regs;
-uint32_t *const i386_esp_ptr = &i386_regs.esp;
+/* Cast suppresses signedness warning (.esp is long, not unsigned long) */
+uint32_t *const i386_esp_ptr = (uint32_t*)&i386_regs.esp;
 # define ARCH_REGS_FOR_GETREGSET i386_regs
 #elif defined(X86_64) || defined(X32)
 /*