cpu_ldst.h, cpu-all.h, bswap.h: Update documentation on ld/st accessors

Add documentation of what the cpu_*_* accessors look like.
Correct some minor errors in the existing documentation of the
direct _p accessor family. Remove the near-duplicate comment
on the _p accessors from cpu-all.h and replace it with a reference
to the comment in bswap.h.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Richard Henderson <rth@twiddle.net>
Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>
Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
Message-id: 1421334118-3287-16-git-send-email-peter.maydell@linaro.org

include/exec/cpu_ldst.h

@@ -23,7 +23,26 @@
  *
  * Used by target op helpers.
  *
- * MMU mode suffixes are defined in target cpu.h.
+ * The syntax for the accessors is:
+ *
+ * load: cpu_ld{sign}{size}_{mmusuffix}(env, ptr)
+ *
+ * store: cpu_st{sign}{size}_{mmusuffix}(env, ptr, val)
+ *
+ * sign is:
+ * (empty): for 32 and 64 bit sizes
+ *   u    : unsigned
+ *   s    : signed
+ *
+ * size is:
+ *   b: 8 bits
+ *   w: 16 bits
+ *   l: 32 bits
+ *   q: 64 bits
+ *
+ * mmusuffix is one of the generic suffixes "data" or "code", or
+ * (for softmmu configs)  a target-specific MMU mode suffix as defined
+ * in target cpu.h.
  */
 #ifndef CPU_LDST_H
 #define CPU_LDST_H