target-i386: Define DR7 bit field constants

Implicit use of dr7 bit field is a little hard to understand,
so define constants for them and use them consistently.

Signed-off-by: liguang <lig.fnst@cn.fujitsu.com>
Signed-off-by: Andreas Färber <afaerber@suse.de>
target-i386: Introduce hw_{local,global}_breakpoint_enabled()

hw_breakpoint_enabled() returned a bit field indicating whether a local
breakpoint and/or global breakpoint was enabled. Avoid this number magic
by using explicit boolean helper functions hw_local_breakpoint_enabled()
and hw_global_breakpoint_enabled(), to aid readability.

Reuse them for the hw_breakpoint_enabled() implementation and change
its return type to bool.

While at it, fix Coding Style issues (missing braces).

Signed-off-by: liguang <lig.fnst@cn.fujitsu.com>
Signed-off-by: Andreas Färber <afaerber@suse.de>
target-i386: Avoid goto in hw_breakpoint_insert()

  "Go To Statement Considered Harmful" -- E. Dijkstra

To avoid an unnecessary goto within the switch statement, move
watchpoint insertion out of the switch statement. Improves readability.

While at it, fix Coding Style issues (missing braces, indentation).

Signed-off-by: liguang <lig.fnst@cn.fujitsu.com>
Signed-off-by: Andreas Färber <afaerber@suse.de>
target-i386: Use switch in check_hw_breakpoints()

Replace an if statement using magic numbers for breakpoint type with a
more explicit switch statement. This is to aid readability.

Change the return type and force_dr6_update argument type to bool.

While at it, fix Coding Style issues (missing braces).

Signed-off-by: liguang <lig.fnst@cn.fujitsu.com>
Signed-off-by: Andreas Färber <afaerber@suse.de>