ARM: mvebu: declare asm symbols as character arrays in pmsu.c

With CONFIG_FORTIFY_SOURCE, memcpy uses the declared size of operands to
detect buffer overflows.  If src or dest is declared as a char, attempts to
copy more than byte will result in a fortify_panic().

Address this problem in mvebu_setup_boot_addr_wa() by declaring
mvebu_boot_wa_start and mvebu_boot_wa_end as character arrays.  Also remove
a couple addressof operators to avoid "arithmetic on pointer to an
incomplete type" compiler error.

See commit 54a7d50b9205 ("x86: mark kprobe templates as character arrays,
not single characters") for a similar fix.

Fixes "detected buffer overflow in memcpy" error during init on some mvebu
systems (armada-370-xp, armada-375):

(fortify_panic) from (mvebu_setup_boot_addr_wa+0xb0/0xb4)
(mvebu_setup_boot_addr_wa) from (mvebu_v7_cpu_pm_init+0x154/0x204)
(mvebu_v7_cpu_pm_init) from (do_one_initcall+0x7c/0x1a8)
(do_one_initcall) from (kernel_init_freeable+0x1bc/0x254)
(kernel_init_freeable) from (kernel_init+0x8/0x114)
(kernel_init) from (ret_from_fork+0x14/0x2c)

Signed-off-by: Ethan Tuttle <ethan@ethantuttle.com>
Tested-by: Ethan Tuttle <ethan@ethantuttle.com>
Signed-off-by: Gregory CLEMENT <gregory.clement@bootlin.com>

arch/arm/mach-mvebu/pmsu.c

@@ -116,8 +116,8 @@ void mvebu_pmsu_set_cpu_boot_addr(int hw_cpu, void *boot_addr)
 		PMSU_BOOT_ADDR_REDIRECT_OFFSET(hw_cpu));
 }
 
-extern unsigned char mvebu_boot_wa_start;
-extern unsigned char mvebu_boot_wa_end;
+extern unsigned char mvebu_boot_wa_start[];
+extern unsigned char mvebu_boot_wa_end[];
 
 /*
  * This function sets up the boot address workaround needed for SMP
@@ -130,7 +130,7 @@ int mvebu_setup_boot_addr_wa(unsigned int crypto_eng_target,
 			     phys_addr_t resume_addr_reg)
 {
 	void __iomem *sram_virt_base;
-	u32 code_len = &mvebu_boot_wa_end - &mvebu_boot_wa_start;
+	u32 code_len = mvebu_boot_wa_end - mvebu_boot_wa_start;
 
 	mvebu_mbus_del_window(BOOTROM_BASE, BOOTROM_SIZE);
 	mvebu_mbus_add_window_by_id(crypto_eng_target, crypto_eng_attribute,