fix(ram_app): Fixed issue ram_app can't use the SPI Flash

1st bootloader won't help to initialize the MSPI & cache properly as it
usually do when loading from flash. And the ram app doesn't have valid
headers.

Since there is no enough space in 2nd bootloader, we replace the
`bootloader_init_spi_flash` in the ram_app (!pure_ram_app), with an
customized alternative of it for the ram_app.

This alternative helps to initialize the MSPI & cache properly, without
the help of 1st bootloader or image headers.

components/bootloader_support/src/bootloader_init.c

@@ -23,7 +23,9 @@
 
 static const char *TAG = "boot";
 
+#if !CONFIG_APP_BUILD_TYPE_RAM
 esp_image_header_t WORD_ALIGNED_ATTR bootloader_image_hdr;
+#endif
 
 void bootloader_clear_bss_section(void)
 {