soc/qualcomm: Remove unused <string.h>

Found using:
diff <(git grep -l '#include <string.h>' -- src/) <(git grep -l 'STRINGIFY\|memcpy\|memmove\|memset\|memcmp\|memchr\|strdup\|strconcat\|strnlen\|strlen\|strchr\|strncpy\|strcpy\|strcmp\|strncmp\|strspn\|strcspn\|strstr\|strtok_r\|strtok\|atol\|strrchr\|skip_atoi\|snprintf' -- src/)|grep '<'

Change-Id: I78f8e115a54f869b990950a1c7d686e0f25033c8
Signed-off-by: Elyes HAOUAS <ehaouas@noos.fr>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/50688
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Kyösti Mälkki <kyosti.malkki@gmail.com>

src/soc/qualcomm/sc7180/carve_out.c

@@ -4,7 +4,6 @@
 #include <soc/mmu_common.h>
 #include <soc/symbols.h>
 #include <device/mmio.h>
-#include <string.h>
 
 #define MODEM_ID_LTE 0x004c5445
 #define MODEM_ID_WIFI 0x57494649

src/soc/qualcomm/sc7180/display/dsi_phy_pll.c

@@ -1,7 +1,6 @@
 /* SPDX-License-Identifier: GPL-2.0-only */
 
 #include <device/mmio.h>
-#include <string.h>
 #include <stdint.h>
 #include <delay.h>
 #include <edid.h>