hv:Replace dynamic memory with static for sbuf

--Config LOG_BUF_SIZE 256KB for per cpu
--Replace 'calloc' with static array for sbuf
--Rename 'alloc_earlylog_sbuf' to 'init_earlylog_sbuf'
--Remove deadcode sbuf_free

v2-->v3:
 -- put the buffer into per_cpu data structure
v1-->v2:
 -- add 'is_early_logbuf' in percpu data structure used for
    check if need to do 'do_copy_earlylog'

Tracked-On: #861
Signed-off-by: Mingqiang Chi <mingqiang.chi@intel.com>
Reviewed-by: Yan, Like <like.yan@intel.com>
Reviewed-by: Jason Chen CJ <jason.cj.chen@intel.com>
Acked-by: Eddie Dong <eddie.dong@intel.com>

hypervisor/arch/x86/Kconfig

@@ -99,6 +99,10 @@ config STACK_SIZE
 	  The size of stacks used by physical cores. Each core uses one stack
 	  for normal operations and another three for specific exceptions.
 
+config LOG_BUF_SIZE
+	hex "Capacity of logbuf for each physical cpu"
+	default 0x40000
+
 config LOG_DESTINATION
 	int "Bitmap of consoles where logs are printed"
 	range 0 7