riscv: clean up the macro format in each header file

There are many different formats in each header now, such as
_ASM_XXX_H, __ASM_XXX_H, _ASM_RISCV_XXX_H, RISCV_XXX_H, etc., This patch
tries to unify the format by using _ASM_RISCV_XXX_H, because the most
header use it now. This patch also adds the conditional to the headers
if they lost it.

Signed-off-by: Zong Li <zong.li@sifive.com>
Signed-off-by: Paul Walmsley <paul.walmsley@sifive.com>

arch/riscv/include/uapi/asm/hwcap.h

@@ -5,8 +5,8 @@
  * Copyright (C) 2012 ARM Ltd.
  * Copyright (C) 2017 SiFive
  */
-#ifndef __UAPI_ASM_HWCAP_H
-#define __UAPI_ASM_HWCAP_H
+#ifndef _UAPI_ASM_RISCV_HWCAP_H
+#define _UAPI_ASM_RISCV_HWCAP_H
 
 /*
  * Linux saves the floating-point registers according to the ISA Linux is
@@ -22,4 +22,4 @@
 #define COMPAT_HWCAP_ISA_D	(1 << ('D' - 'A'))
 #define COMPAT_HWCAP_ISA_C	(1 << ('C' - 'A'))
 
-#endif
+#endif /* _UAPI_ASM_RISCV_HWCAP_H */