Revert "build: Specify -march=btver2 explicitly, for AMD Fam16h processors"

This reverts commit 335c103.

Without -march=btver2 SKL can be used on AMD 15h or earlier and now that
SKL more than fits into 64KiB limit, no need for such options to save a
bit of space.

Signed-off-by: Sergii Dmytruk <[email protected]>

Author: SergiiDmytruk

Makefile

@@ -26,7 +26,7 @@ endif
 # at an arbitrary location, so build it as position independent, but link as
 # non-pie as all relocations are internal and there is no dynamic loader to
 # help.
-CFLAGS  += -Os -g -MMD -MP -march=btver2 -mno-sse -mno-mmx -fpie -fomit-frame-pointer
+CFLAGS  += -Os -g -MMD -MP -mno-sse -mno-mmx -fpie -fomit-frame-pointer
 CFLAGS  += -Iinclude -ffreestanding -fno-common -Wall -Werror
 LDFLAGS += -nostdlib -no-pie -Wl,--build-id=none,--fatal-warnings,--defsym=BITS=$(BITS)